<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <link:roleRef roleURI="http://www.synchronoss.com/role/AccumulatedOtherComprehensiveIncomeLoss" xlink:href="sncr-20180331.xsd#AccumulatedOtherComprehensiveIncomeLoss" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/AccumulatedOtherComprehensiveIncomeLossChangesInAociDetails" xlink:href="sncr-20180331.xsd#AccumulatedOtherComprehensiveIncomeLossChangesInAociDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/AccumulatedOtherComprehensiveIncomeLossTables" xlink:href="sncr-20180331.xsd#AccumulatedOtherComprehensiveIncomeLossTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/AcquisitionsAndDivestitures" xlink:href="sncr-20180331.xsd#AcquisitionsAndDivestitures" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/AcquisitionsAndDivestituresDivestituresDetails" xlink:href="sncr-20180331.xsd#AcquisitionsAndDivestituresDivestituresDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/AcquisitionsAndDivestituresIntralinksDetails" xlink:href="sncr-20180331.xsd#AcquisitionsAndDivestituresIntralinksDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidation" xlink:href="sncr-20180331.xsd#BasisOfPresentationAndConsolidation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationAssetsAndLiabilitiesDetails" xlink:href="sncr-20180331.xsd#BasisOfPresentationAndConsolidationAssetsAndLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationDisaggregationOfRevenueDetails" xlink:href="sncr-20180331.xsd#BasisOfPresentationAndConsolidationDisaggregationOfRevenueDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationEquityImpactDetails" xlink:href="sncr-20180331.xsd#BasisOfPresentationAndConsolidationEquityImpactDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationNarrativeDetails" xlink:href="sncr-20180331.xsd#BasisOfPresentationAndConsolidationNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationPolicies" xlink:href="sncr-20180331.xsd#BasisOfPresentationAndConsolidationPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationScheduleOfEffectOfNewAccountingPronouncementDetails" xlink:href="sncr-20180331.xsd#BasisOfPresentationAndConsolidationScheduleOfEffectOfNewAccountingPronouncementDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationScheduleOfIncomeStatementEffectOfNewAccountingPronouncementsDetails" xlink:href="sncr-20180331.xsd#BasisOfPresentationAndConsolidationScheduleOfIncomeStatementEffectOfNewAccountingPronouncementsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationTables" xlink:href="sncr-20180331.xsd#BasisOfPresentationAndConsolidationTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/CommitmentsAndContingencies" xlink:href="sncr-20180331.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/CommitmentsAndContingenciesDetails" xlink:href="sncr-20180331.xsd#CommitmentsAndContingenciesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/CondensedConsolidatedBalanceSheetsUnaudited" xlink:href="sncr-20180331.xsd#CondensedConsolidatedBalanceSheetsUnaudited" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/CondensedConsolidatedBalanceSheetsUnauditedParenthetical" xlink:href="sncr-20180331.xsd#CondensedConsolidatedBalanceSheetsUnauditedParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited" xlink:href="sncr-20180331.xsd#CondensedConsolidatedStatementsOfCashFlowsUnaudited" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/CondensedConsolidatedStatementsOfComprehensiveLossUnauditedStatement" xlink:href="sncr-20180331.xsd#CondensedConsolidatedStatementsOfComprehensiveLossUnauditedStatement" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/CondensedConsolidatedStatementsOfOperationsUnaudited" xlink:href="sncr-20180331.xsd#CondensedConsolidatedStatementsOfOperationsUnaudited" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/Debt" xlink:href="sncr-20180331.xsd#Debt" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/DebtConvertibleSeniorNotesDetails" xlink:href="sncr-20180331.xsd#DebtConvertibleSeniorNotesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/DebtInterestExpenseDetails" xlink:href="sncr-20180331.xsd#DebtInterestExpenseDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/DebtScheduleOfDebtDetails" xlink:href="sncr-20180331.xsd#DebtScheduleOfDebtDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/DebtTables" xlink:href="sncr-20180331.xsd#DebtTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/DescriptionOfBusiness" xlink:href="sncr-20180331.xsd#DescriptionOfBusiness" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/DocumentAndEntityInformation" xlink:href="sncr-20180331.xsd#DocumentAndEntityInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/EarningsPerCommonShare" xlink:href="sncr-20180331.xsd#EarningsPerCommonShare" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/EarningsPerCommonShareDetails" xlink:href="sncr-20180331.xsd#EarningsPerCommonShareDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/EarningsPerCommonShareTables" xlink:href="sncr-20180331.xsd#EarningsPerCommonShareTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/FairValueMeasurementsOfAssetsAndLiabilities" xlink:href="sncr-20180331.xsd#FairValueMeasurementsOfAssetsAndLiabilities" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/FairValueMeasurementsOfAssetsAndLiabilitiesAfsSecuritiesDetails" xlink:href="sncr-20180331.xsd#FairValueMeasurementsOfAssetsAndLiabilitiesAfsSecuritiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/FairValueMeasurementsOfAssetsAndLiabilitiesAfsSecuritiesExpectedMaturitiesDetails" xlink:href="sncr-20180331.xsd#FairValueMeasurementsOfAssetsAndLiabilitiesAfsSecuritiesExpectedMaturitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/FairValueMeasurementsOfAssetsAndLiabilitiesAfsSecuritiesInUnrealizedLossPositionDetails" xlink:href="sncr-20180331.xsd#FairValueMeasurementsOfAssetsAndLiabilitiesAfsSecuritiesInUnrealizedLossPositionDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/FairValueMeasurementsOfAssetsAndLiabilitiesHierarchyDetails" xlink:href="sncr-20180331.xsd#FairValueMeasurementsOfAssetsAndLiabilitiesHierarchyDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/FairValueMeasurementsOfAssetsAndLiabilitiesLevel3RedeemableNoncontrollingInterestsDetails" xlink:href="sncr-20180331.xsd#FairValueMeasurementsOfAssetsAndLiabilitiesLevel3RedeemableNoncontrollingInterestsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/FairValueMeasurementsOfAssetsAndLiabilitiesTables" xlink:href="sncr-20180331.xsd#FairValueMeasurementsOfAssetsAndLiabilitiesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/IncomeTaxes" xlink:href="sncr-20180331.xsd#IncomeTaxes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/IncomeTaxesDetails" xlink:href="sncr-20180331.xsd#IncomeTaxesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/Investments" xlink:href="sncr-20180331.xsd#Investments" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/InvestmentsDetails" xlink:href="sncr-20180331.xsd#InvestmentsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/InvestmentsEquityMethodInvestmentDetails" xlink:href="sncr-20180331.xsd#InvestmentsEquityMethodInvestmentDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/InvestmentsNoteReceivableDetails" xlink:href="sncr-20180331.xsd#InvestmentsNoteReceivableDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/InvestmentsTables" xlink:href="sncr-20180331.xsd#InvestmentsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/Restructuring" xlink:href="sncr-20180331.xsd#Restructuring" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/RestructuringDetails" xlink:href="sncr-20180331.xsd#RestructuringDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/RestructuringTables" xlink:href="sncr-20180331.xsd#RestructuringTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/StockholdersEquity" xlink:href="sncr-20180331.xsd#StockholdersEquity" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/StockholdersEquityBlackScholesAssumptionsDetails" xlink:href="sncr-20180331.xsd#StockholdersEquityBlackScholesAssumptionsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/StockholdersEquityEsppAndOtherDisclosuresDetails" xlink:href="sncr-20180331.xsd#StockholdersEquityEsppAndOtherDisclosuresDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/StockholdersEquityNarrativeDetails" xlink:href="sncr-20180331.xsd#StockholdersEquityNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/StockholdersEquityRestrictedStockDetails" xlink:href="sncr-20180331.xsd#StockholdersEquityRestrictedStockDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/StockholdersEquityStockBasedCompensationDetails" xlink:href="sncr-20180331.xsd#StockholdersEquityStockBasedCompensationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/StockholdersEquityStockOptionsDetails" xlink:href="sncr-20180331.xsd#StockholdersEquityStockOptionsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/StockholdersEquityTables" xlink:href="sncr-20180331.xsd#StockholdersEquityTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/StockholdersEquityTreasuryStockDetails" xlink:href="sncr-20180331.xsd#StockholdersEquityTreasuryStockDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/SubsequentEventsReview" xlink:href="sncr-20180331.xsd#SubsequentEventsReview" xlink:type="simple" />
  <link:roleRef roleURI="http://www.synchronoss.com/role/SubsequentEventsReviewDetails" xlink:href="sncr-20180331.xsd#SubsequentEventsReviewDetails" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/AccumulatedOtherComprehensiveIncomeLoss" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/AccumulatedOtherComprehensiveIncomeLossChangesInAociDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_E0F01C881B9087362549DCC13F17805E" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_A65E7D1ED1B5835C7DD7DCC13F1536F2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_E0F01C881B9087362549DCC13F17805E" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_A65E7D1ED1B5835C7DD7DCC13F1536F2" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_F491F08B6C7313E976AEDCC13F157C0E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_A65E7D1ED1B5835C7DD7DCC13F1536F2" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_F491F08B6C7313E976AEDCC13F157C0E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_A9BB0168B58CF609BD0CDCC13F15B947_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_F491F08B6C7313E976AEDCC13F157C0E" xlink:to="loc_us-gaap_EquityComponentDomain_A9BB0168B58CF609BD0CDCC13F15B947_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_A9BB0168B58CF609BD0CDCC13F15B947" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_F491F08B6C7313E976AEDCC13F157C0E" xlink:to="loc_us-gaap_EquityComponentDomain_A9BB0168B58CF609BD0CDCC13F15B947" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_07851211968424A1F72EDCC13F169C14" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_A9BB0168B58CF609BD0CDCC13F15B947" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_07851211968424A1F72EDCC13F169C14" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedTranslationAdjustmentMember" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_07413F32B2259E431037DCC13F162529" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_07851211968424A1F72EDCC13F169C14" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_07413F32B2259E431037DCC13F162529" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_AccumulatedNetGainLossOnIntraEntityForeignCurrencyTransactionsMember" xlink:label="loc_sncr_AccumulatedNetGainLossOnIntraEntityForeignCurrencyTransactionsMember_FC49234FFEDCB377F28DDCC13F16F169" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_07851211968424A1F72EDCC13F169C14" xlink:to="loc_sncr_AccumulatedNetGainLossOnIntraEntityForeignCurrencyTransactionsMember_FC49234FFEDCB377F28DDCC13F16F169" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_D51D278528EC5065BAD6DCC13F161A44" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_07851211968424A1F72EDCC13F169C14" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_D51D278528EC5065BAD6DCC13F161A44" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_7B6A9D6E871B08266F12DCC13F17950B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_E0F01C881B9087362549DCC13F17805E" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_7B6A9D6E871B08266F12DCC13F17950B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="loc_us-gaap_StockholdersEquity_4B1C2FAC695E0ED76E3EDCC13F177D47" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_7B6A9D6E871B08266F12DCC13F17950B" xlink:to="loc_us-gaap_StockholdersEquity_4B1C2FAC695E0ED76E3EDCC13F177D47" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent_D8116BEEABBC05135493DCC13F17C76C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_7B6A9D6E871B08266F12DCC13F17950B" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTaxPortionAttributableToParent_D8116BEEABBC05135493DCC13F17C76C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_BBEB7343472865885E4EDCC13F18C6EF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_7B6A9D6E871B08266F12DCC13F17950B" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTaxPortionAttributableToParent1_BBEB7343472865885E4EDCC13F18C6EF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_EADFC6EF03DCFF7E5F86DCC13F181C4F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_7B6A9D6E871B08266F12DCC13F17950B" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_EADFC6EF03DCFF7E5F86DCC13F181C4F" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/AccumulatedOtherComprehensiveIncomeLossTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/AcquisitionsAndDivestitures" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/AcquisitionsAndDivestituresDivestituresDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_B5E73290E5B0FB823D6DDC35EC556079" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_3633D270CD3AE1B3B2EEDC35EC545A19" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_B5E73290E5B0FB823D6DDC35EC556079" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_3633D270CD3AE1B3B2EEDC35EC545A19" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_B903CA2111D0074C3770DC35EC542D1E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_3633D270CD3AE1B3B2EEDC35EC545A19" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_B903CA2111D0074C3770DC35EC542D1E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_AEBBBA8CC311FE51A74BDC35EC55F747_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_B903CA2111D0074C3770DC35EC542D1E" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_AEBBBA8CC311FE51A74BDC35EC55F747_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_AEBBBA8CC311FE51A74BDC35EC55F747" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_B903CA2111D0074C3770DC35EC542D1E" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_AEBBBA8CC311FE51A74BDC35EC55F747" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_DivestitureofSpeechCycleMember" xlink:label="loc_sncr_DivestitureofSpeechCycleMember_339F2FF3130FE6088D74DC35EC55A54A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_AEBBBA8CC311FE51A74BDC35EC55F747" xlink:to="loc_sncr_DivestitureofSpeechCycleMember_339F2FF3130FE6088D74DC35EC55A54A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_5A534DEEABA3CD1C0FF2DC35EC552AFE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_B5E73290E5B0FB823D6DDC35EC556079" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_5A534DEEABA3CD1C0FF2DC35EC552AFE" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_DisposalGroupIncludingDiscontinuedOperationPeriodofTransitionServicesAgreement" xlink:label="loc_sncr_DisposalGroupIncludingDiscontinuedOperationPeriodofTransitionServicesAgreement_6BD93D20116728F35FE1DC35EC560416" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_B5E73290E5B0FB823D6DDC35EC556079" xlink:to="loc_sncr_DisposalGroupIncludingDiscontinuedOperationPeriodofTransitionServicesAgreement_6BD93D20116728F35FE1DC35EC560416" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal" xlink:label="loc_us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_B9E6189729A1ED4EA17EDC35EC56203C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_B5E73290E5B0FB823D6DDC35EC556079" xlink:to="loc_us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_B9E6189729A1ED4EA17EDC35EC56203C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/AcquisitionsAndDivestituresIntralinksDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_8C48507D46D956528823421B7C2ED72D" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_55E7248E70C4A0EDD9B9421B7C2A62A8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_8C48507D46D956528823421B7C2ED72D" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_55E7248E70C4A0EDD9B9421B7C2A62A8" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_70E90BFFF6D16B25C668423A9F66D6F6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_55E7248E70C4A0EDD9B9421B7C2A62A8" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_70E90BFFF6D16B25C668423A9F66D6F6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_0CA1DE8EE38B050446FE423A9F67AB55_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_70E90BFFF6D16B25C668423A9F66D6F6" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_0CA1DE8EE38B050446FE423A9F67AB55_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_0CA1DE8EE38B050446FE423A9F67AB55" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_70E90BFFF6D16B25C668423A9F66D6F6" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_0CA1DE8EE38B050446FE423A9F67AB55" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_18BA5C5A6D7976AD465E423A9FB1D494" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_0CA1DE8EE38B050446FE423A9F67AB55" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_18BA5C5A6D7976AD465E423A9FB1D494" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_ED02BC1FF2254E791386421B7C2A4A50" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_55E7248E70C4A0EDD9B9421B7C2A62A8" xlink:to="loc_dei_LegalEntityAxis_ED02BC1FF2254E791386421B7C2A4A50" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_5AC3485783CBFBD91FD2421B7C2AED63_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_ED02BC1FF2254E791386421B7C2A4A50" xlink:to="loc_dei_EntityDomain_5AC3485783CBFBD91FD2421B7C2AED63_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_5AC3485783CBFBD91FD2421B7C2AED63" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_ED02BC1FF2254E791386421B7C2A4A50" xlink:to="loc_dei_EntityDomain_5AC3485783CBFBD91FD2421B7C2AED63" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_ImpalaMember" xlink:label="loc_sncr_ImpalaMember_5FA23C9F23A4A586F2A8421B7C2B0C77" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_5AC3485783CBFBD91FD2421B7C2AED63" xlink:to="loc_sncr_ImpalaMember_5FA23C9F23A4A586F2A8421B7C2B0C77" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityAxis" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_9A18EB48628E83BFABDC421B7C2BDD7F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_55E7248E70C4A0EDD9B9421B7C2A62A8" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_9A18EB48628E83BFABDC421B7C2BDD7F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_8266667BF2C5EEC2AC54421B7C2B7B94_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_9A18EB48628E83BFABDC421B7C2BDD7F" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_8266667BF2C5EEC2AC54421B7C2B7B94_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_8266667BF2C5EEC2AC54421B7C2B7B94" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_9A18EB48628E83BFABDC421B7C2BDD7F" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_8266667BF2C5EEC2AC54421B7C2B7B94" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_GoldmanSachsBankUSAMember" xlink:label="loc_sncr_GoldmanSachsBankUSAMember_0BE55FB10B4F1E89AF8A421B7C2B07FF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_8266667BF2C5EEC2AC54421B7C2B7B94" xlink:to="loc_sncr_GoldmanSachsBankUSAMember_0BE55FB10B4F1E89AF8A421B7C2B07FF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_1749D742E74D2B678C80421B7C2C773E" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_55E7248E70C4A0EDD9B9421B7C2A62A8" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_1749D742E74D2B678C80421B7C2C773E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_D3FA66CE74586A5C9DBB421B7C2C0B43_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_1749D742E74D2B678C80421B7C2C773E" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_D3FA66CE74586A5C9DBB421B7C2C0B43_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_D3FA66CE74586A5C9DBB421B7C2C0B43" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_1749D742E74D2B678C80421B7C2C773E" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_D3FA66CE74586A5C9DBB421B7C2C0B43" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_IntralinksHoldingsInc.Member" xlink:label="loc_sncr_IntralinksHoldingsInc.Member_747B26AF0C9D00A3F920421B7C2C374A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_D3FA66CE74586A5C9DBB421B7C2C0B43" xlink:to="loc_sncr_IntralinksHoldingsInc.Member_747B26AF0C9D00A3F920421B7C2C374A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_3D5B5218F95D6229D8ED421B7C2C263D" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_55E7248E70C4A0EDD9B9421B7C2A62A8" xlink:to="loc_us-gaap_CreditFacilityAxis_3D5B5218F95D6229D8ED421B7C2C263D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_39BA7645D8C9416498BD421B7C2D7B4F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_3D5B5218F95D6229D8ED421B7C2C263D" xlink:to="loc_us-gaap_CreditFacilityDomain_39BA7645D8C9416498BD421B7C2D7B4F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_39BA7645D8C9416498BD421B7C2D7B4F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_3D5B5218F95D6229D8ED421B7C2C263D" xlink:to="loc_us-gaap_CreditFacilityDomain_39BA7645D8C9416498BD421B7C2D7B4F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SecuredDebtMember" xlink:label="loc_us-gaap_SecuredDebtMember_EB5018C5EA6A75565C73421B7C2D43F5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_39BA7645D8C9416498BD421B7C2D7B4F" xlink:to="loc_us-gaap_SecuredDebtMember_EB5018C5EA6A75565C73421B7C2D43F5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_65758D8B2D8BF9DD8FDB421B7C2DA6B3" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_55E7248E70C4A0EDD9B9421B7C2A62A8" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_65758D8B2D8BF9DD8FDB421B7C2DA6B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_03ED1B9DDB0A82267E8F421B7C2DC4C7_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_65758D8B2D8BF9DD8FDB421B7C2DA6B3" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_03ED1B9DDB0A82267E8F421B7C2DC4C7_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_03ED1B9DDB0A82267E8F421B7C2DC4C7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_65758D8B2D8BF9DD8FDB421B7C2DA6B3" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_03ED1B9DDB0A82267E8F421B7C2DC4C7" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_IntralinksHoldingsInc.Member" xlink:label="loc_sncr_IntralinksHoldingsInc.Member_E4AC38DF7779CA9E5134421B7C2EB50A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_03ED1B9DDB0A82267E8F421B7C2DC4C7" xlink:to="loc_sncr_IntralinksHoldingsInc.Member_E4AC38DF7779CA9E5134421B7C2EB50A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_CE217428C26E92688AF1421B7C2EDC75" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_8C48507D46D956528823421B7C2ED72D" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_CE217428C26E92688AF1421B7C2EDC75" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_82078AC1D8213029F5AF421B7C2E8A04" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_8C48507D46D956528823421B7C2ED72D" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_82078AC1D8213029F5AF421B7C2E8A04" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_98031A1CEC2788786F7E421B7C2FC053" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_8C48507D46D956528823421B7C2ED72D" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_98031A1CEC2788786F7E421B7C2FC053" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromLongTermLinesOfCredit" xlink:label="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_EE10B705FC1695F5EC03421B7C2F7175" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_8C48507D46D956528823421B7C2ED72D" xlink:to="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_EE10B705FC1695F5EC03421B7C2F7175" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_5FC2449FEDA48559B6BF421B7C2FC6A6" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_8C48507D46D956528823421B7C2ED72D" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_5FC2449FEDA48559B6BF421B7C2FC6A6" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationAssetsAndLiabilitiesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationDisaggregationOfRevenueDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_D45303B3C1D83704731A42355BF29CE9" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisaggregationOfRevenueTable" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_85AC8311FD823C2BA11342355BEFB5F7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_D45303B3C1D83704731A42355BF29CE9" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_85AC8311FD823C2BA11342355BEFB5F7" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProductOrServiceAxis" xlink:label="loc_us-gaap_ProductOrServiceAxis_860D1AF157BB2FDBF6EF42355BEF03E8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_85AC8311FD823C2BA11342355BEFB5F7" xlink:to="loc_us-gaap_ProductOrServiceAxis_860D1AF157BB2FDBF6EF42355BEF03E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProductsAndServicesDomain" xlink:label="loc_us-gaap_ProductsAndServicesDomain_F128130ACF29E11AB60842355BF0CB6D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ProductOrServiceAxis_860D1AF157BB2FDBF6EF42355BEF03E8" xlink:to="loc_us-gaap_ProductsAndServicesDomain_F128130ACF29E11AB60842355BF0CB6D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProductsAndServicesDomain" xlink:label="loc_us-gaap_ProductsAndServicesDomain_F128130ACF29E11AB60842355BF0CB6D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ProductOrServiceAxis_860D1AF157BB2FDBF6EF42355BEF03E8" xlink:to="loc_us-gaap_ProductsAndServicesDomain_F128130ACF29E11AB60842355BF0CB6D" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_CloudMember" xlink:label="loc_sncr_CloudMember_F2F78E1AE31868233C3642355BEFA36F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductsAndServicesDomain_F128130ACF29E11AB60842355BF0CB6D" xlink:to="loc_sncr_CloudMember_F2F78E1AE31868233C3642355BEFA36F" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_DigitalMember" xlink:label="loc_sncr_DigitalMember_B5D2D58A561CCA7326BB42355BEF572B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductsAndServicesDomain_F128130ACF29E11AB60842355BF0CB6D" xlink:to="loc_sncr_DigitalMember_B5D2D58A561CCA7326BB42355BEF572B" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_MessagingMember" xlink:label="loc_sncr_MessagingMember_742E8B0E04E1A642753C42355BEF772A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductsAndServicesDomain_F128130ACF29E11AB60842355BF0CB6D" xlink:to="loc_sncr_MessagingMember_742E8B0E04E1A642753C42355BEF772A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_E30A2A6FD84CDAD4CBA842355BF0BCCF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_85AC8311FD823C2BA11342355BEFB5F7" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_E30A2A6FD84CDAD4CBA842355BF0BCCF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_409CFBBC488AAAECBF0C42355BF0A5F0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_E30A2A6FD84CDAD4CBA842355BF0BCCF" xlink:to="loc_us-gaap_SegmentDomain_409CFBBC488AAAECBF0C42355BF0A5F0_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_409CFBBC488AAAECBF0C42355BF0A5F0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_E30A2A6FD84CDAD4CBA842355BF0BCCF" xlink:to="loc_us-gaap_SegmentDomain_409CFBBC488AAAECBF0C42355BF0A5F0" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_ProfessionalServicesMember" xlink:label="loc_sncr_ProfessionalServicesMember_372A9C44165B0750BA7142355BF0D3E0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_409CFBBC488AAAECBF0C42355BF0A5F0" xlink:to="loc_sncr_ProfessionalServicesMember_372A9C44165B0750BA7142355BF0D3E0" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_TransactionServicesMember" xlink:label="loc_sncr_TransactionServicesMember_F808FD79112803C90A6042355BF003F1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_409CFBBC488AAAECBF0C42355BF0A5F0" xlink:to="loc_sncr_TransactionServicesMember_F808FD79112803C90A6042355BF003F1" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_SubscriptionServicesMember" xlink:label="loc_sncr_SubscriptionServicesMember_44353125733C272D70E942355BF1DE7C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_409CFBBC488AAAECBF0C42355BF0A5F0" xlink:to="loc_sncr_SubscriptionServicesMember_44353125733C272D70E942355BF1DE7C" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_LicenseMember" xlink:label="loc_sncr_LicenseMember_748A369CD2FDF17ED42442355BF1B050" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_409CFBBC488AAAECBF0C42355BF0A5F0" xlink:to="loc_sncr_LicenseMember_748A369CD2FDF17ED42442355BF1B050" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementGeographicalAxis" xlink:label="loc_us-gaap_StatementGeographicalAxis_99FD17EF3468C467CA9342355BF11B29" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_85AC8311FD823C2BA11342355BEFB5F7" xlink:to="loc_us-gaap_StatementGeographicalAxis_99FD17EF3468C467CA9342355BF11B29" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentGeographicalDomain" xlink:label="loc_us-gaap_SegmentGeographicalDomain_E32CD2FB8FDFAA3DF80542355BF105F3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementGeographicalAxis_99FD17EF3468C467CA9342355BF11B29" xlink:to="loc_us-gaap_SegmentGeographicalDomain_E32CD2FB8FDFAA3DF80542355BF105F3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SegmentGeographicalDomain" xlink:label="loc_us-gaap_SegmentGeographicalDomain_E32CD2FB8FDFAA3DF80542355BF105F3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementGeographicalAxis_99FD17EF3468C467CA9342355BF11B29" xlink:to="loc_us-gaap_SegmentGeographicalDomain_E32CD2FB8FDFAA3DF80542355BF105F3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AmericasMember" xlink:label="loc_us-gaap_AmericasMember_AA15BCE98545EED9376B42355BF151E5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentGeographicalDomain_E32CD2FB8FDFAA3DF80542355BF105F3" xlink:to="loc_us-gaap_AmericasMember_AA15BCE98545EED9376B42355BF151E5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AsiaPacificMember" xlink:label="loc_us-gaap_AsiaPacificMember_124D5B902BDC6DB7B46842355BF15C76" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentGeographicalDomain_E32CD2FB8FDFAA3DF80542355BF105F3" xlink:to="loc_us-gaap_AsiaPacificMember_124D5B902BDC6DB7B46842355BF15C76" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EMEAMember" xlink:label="loc_us-gaap_EMEAMember_F3A93E5D3437FCBE25BC42355BF2C04B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentGeographicalDomain_E32CD2FB8FDFAA3DF80542355BF105F3" xlink:to="loc_us-gaap_EMEAMember_F3A93E5D3437FCBE25BC42355BF2C04B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaap_Revenues_157ECE834EE10C13D70942355BF225C7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_D45303B3C1D83704731A42355BF29CE9" xlink:to="loc_us-gaap_Revenues_157ECE834EE10C13D70942355BF225C7" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationEquityImpactDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems" xlink:label="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_A0AA898238D3BFF89EE34CBD62E61463" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable" xlink:label="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable_80CF09AB5967F2DD75684CBD62D80E41" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_A0AA898238D3BFF89EE34CBD62E61463" xlink:to="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable_80CF09AB5967F2DD75684CBD62D80E41" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_74E7A3D264FCE3D4564E4CBC85355A2E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable_80CF09AB5967F2DD75684CBD62D80E41" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_74E7A3D264FCE3D4564E4CBC85355A2E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_1BED361EF398B583470A4CBC85356DAE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_74E7A3D264FCE3D4564E4CBC85355A2E" xlink:to="loc_us-gaap_TypeOfAdoptionMember_1BED361EF398B583470A4CBC85356DAE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_1BED361EF398B583470A4CBC85356DAE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_74E7A3D264FCE3D4564E4CBC85355A2E" xlink:to="loc_us-gaap_TypeOfAdoptionMember_1BED361EF398B583470A4CBC85356DAE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountingStandardsUpdate201409Member" xlink:label="loc_us-gaap_AccountingStandardsUpdate201409Member_CE78D49739EAF979D08A4CBC85351835" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_1BED361EF398B583470A4CBC85356DAE" xlink:to="loc_us-gaap_AccountingStandardsUpdate201409Member_CE78D49739EAF979D08A4CBC85351835" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_F0224F8DD3D6BEA42F044CBC85364FA1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable_80CF09AB5967F2DD75684CBD62D80E41" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_F0224F8DD3D6BEA42F044CBC85364FA1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_102E0886867BB7542BF44CBC853610ED_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_F0224F8DD3D6BEA42F044CBC85364FA1" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_102E0886867BB7542BF44CBC853610ED_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_102E0886867BB7542BF44CBC853610ED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_F0224F8DD3D6BEA42F044CBC85364FA1" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_102E0886867BB7542BF44CBC853610ED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member" xlink:label="loc_us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member_D01AE8C4072806F05EFB4CBC85360B63" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_102E0886867BB7542BF44CBC853610ED" xlink:to="loc_us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member_D01AE8C4072806F05EFB4CBC85360B63" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CumulativeEffectOnRetainedEarningsNetOfTax1" xlink:label="loc_us-gaap_CumulativeEffectOnRetainedEarningsNetOfTax1_3498D9A6258DAD53D46D4CBC8534368F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_A0AA898238D3BFF89EE34CBD62E61463" xlink:to="loc_us-gaap_CumulativeEffectOnRetainedEarningsNetOfTax1_3498D9A6258DAD53D46D4CBC8534368F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_63FF3C7CA4BC74FD86B74CBC85373D40" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_A0AA898238D3BFF89EE34CBD62E61463" xlink:to="loc_us-gaap_NetIncomeLoss_63FF3C7CA4BC74FD86B74CBC85373D40" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_97B7BBBFDD94E5B969B64CBC8537082D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_A0AA898238D3BFF89EE34CBD62E61463" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_97B7BBBFDD94E5B969B64CBC8537082D" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_2D6B8D4F2C4CEE797F1D43381E731294" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisaggregationOfRevenueTable" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_2FB00F21A47133487B3343381E71492D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_2D6B8D4F2C4CEE797F1D43381E731294" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_2FB00F21A47133487B3343381E71492D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_71E288109C30175F64E243381E722009" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_2FB00F21A47133487B3343381E71492D" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_71E288109C30175F64E243381E722009" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_C55E48329C06851F41E943381E725801_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_71E288109C30175F64E243381E722009" xlink:to="loc_us-gaap_TypeOfAdoptionMember_C55E48329C06851F41E943381E725801_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_C55E48329C06851F41E943381E725801" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_71E288109C30175F64E243381E722009" xlink:to="loc_us-gaap_TypeOfAdoptionMember_C55E48329C06851F41E943381E725801" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountingStandardsUpdate201409Member" xlink:label="loc_us-gaap_AccountingStandardsUpdate201409Member_5E4AD90B364CE09A7F9E43381E72C44F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_C55E48329C06851F41E943381E725801" xlink:to="loc_us-gaap_AccountingStandardsUpdate201409Member_5E4AD90B364CE09A7F9E43381E72C44F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_2E1B7A54B1435D16525143381E734684" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_2FB00F21A47133487B3343381E71492D" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_2E1B7A54B1435D16525143381E734684" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_49AB7ABF3382E46180B243381E734B88_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_2E1B7A54B1435D16525143381E734684" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_49AB7ABF3382E46180B243381E734B88_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_49AB7ABF3382E46180B243381E734B88" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_2E1B7A54B1435D16525143381E734684" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_49AB7ABF3382E46180B243381E734B88" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member" xlink:label="loc_us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member_76E58E1A8128E599BD4143381E737ACA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_49AB7ABF3382E46180B243381E734B88" xlink:to="loc_us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member_76E58E1A8128E599BD4143381E737ACA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_219FC26365D7A5904FF543381E74D48F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_2D6B8D4F2C4CEE797F1D43381E731294" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_219FC26365D7A5904FF543381E74D48F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CapitalizedContractCostNet" xlink:label="loc_us-gaap_CapitalizedContractCostNet_D3748DBE1E45916EBE3743381E74074D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_2D6B8D4F2C4CEE797F1D43381E731294" xlink:to="loc_us-gaap_CapitalizedContractCostNet_D3748DBE1E45916EBE3743381E74074D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaap_Revenues_0CAC6182ADEE4430CAFB43381E74B763" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_2D6B8D4F2C4CEE797F1D43381E731294" xlink:to="loc_us-gaap_Revenues_0CAC6182ADEE4430CAFB43381E74B763" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligation" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_69D56592CC5A7138081E43381E7416D1" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_2D6B8D4F2C4CEE797F1D43381E731294" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_69D56592CC5A7138081E43381E7416D1" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_RevenueRemainingPerformanceObligationExpectedTimingofSatisfactionPercent" xlink:label="loc_sncr_RevenueRemainingPerformanceObligationExpectedTimingofSatisfactionPercent_181882B66FBE0220A96443381E74B70E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_2D6B8D4F2C4CEE797F1D43381E731294" xlink:to="loc_sncr_RevenueRemainingPerformanceObligationExpectedTimingofSatisfactionPercent_181882B66FBE0220A96443381E74B70E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod_52F1D47121A1CF27525443381E7559BC" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_2D6B8D4F2C4CEE797F1D43381E731294" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod_52F1D47121A1CF27525443381E7559BC" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationScheduleOfEffectOfNewAccountingPronouncementDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems" xlink:label="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_6BBD524801232A36CA5A4CC03B82C6B6" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable" xlink:label="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable_9BCA96857C8F1F602DF94CC03B7F9C40" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_6BBD524801232A36CA5A4CC03B82C6B6" xlink:to="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable_9BCA96857C8F1F602DF94CC03B7F9C40" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_7833502788A6F3A4771C4CC03B7FBC47" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable_9BCA96857C8F1F602DF94CC03B7F9C40" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_7833502788A6F3A4771C4CC03B7FBC47" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_4D495A0210963A19C67B4CC03B807DCD_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_7833502788A6F3A4771C4CC03B7FBC47" xlink:to="loc_us-gaap_TypeOfAdoptionMember_4D495A0210963A19C67B4CC03B807DCD_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_4D495A0210963A19C67B4CC03B807DCD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_7833502788A6F3A4771C4CC03B7FBC47" xlink:to="loc_us-gaap_TypeOfAdoptionMember_4D495A0210963A19C67B4CC03B807DCD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountingStandardsUpdate201409Member" xlink:label="loc_us-gaap_AccountingStandardsUpdate201409Member_558704AFD10C9ABDD1DA4CC03B807720" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_4D495A0210963A19C67B4CC03B807DCD" xlink:to="loc_us-gaap_AccountingStandardsUpdate201409Member_558704AFD10C9ABDD1DA4CC03B807720" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_23211D56FB928E4792F84CC03B800374" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable_9BCA96857C8F1F602DF94CC03B7F9C40" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_23211D56FB928E4792F84CC03B800374" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_59FF39C5F6671B8C09F64CC03B80F025_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_23211D56FB928E4792F84CC03B800374" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_59FF39C5F6671B8C09F64CC03B80F025_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_59FF39C5F6671B8C09F64CC03B80F025" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_23211D56FB928E4792F84CC03B800374" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_59FF39C5F6671B8C09F64CC03B80F025" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member" xlink:label="loc_us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member_560974EF3E0E5E50BB9E4CC03B81C2CC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_59FF39C5F6671B8C09F64CC03B80F025" xlink:to="loc_us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member_560974EF3E0E5E50BB9E4CC03B81C2CC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member" xlink:label="loc_us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member_CA3AC08AD0AEAB9CD23B4CC03B81C7EC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_59FF39C5F6671B8C09F64CC03B80F025" xlink:to="loc_us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member_CA3AC08AD0AEAB9CD23B4CC03B81C7EC" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_CalculatedunderRevenueGuidanceinEffectAfterTopic606Member" xlink:label="loc_sncr_CalculatedunderRevenueGuidanceinEffectAfterTopic606Member_6E353FF29BE4E987272C4CC03B814CB1" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_59FF39C5F6671B8C09F64CC03B80F025" xlink:to="loc_sncr_CalculatedunderRevenueGuidanceinEffectAfterTopic606Member_6E353FF29BE4E987272C4CC03B814CB1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AssetsAbstract" xlink:label="loc_us-gaap_AssetsAbstract_3D4799439E7B678599744CC03B829D6A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_6BBD524801232A36CA5A4CC03B82C6B6" xlink:to="loc_us-gaap_AssetsAbstract_3D4799439E7B678599744CC03B829D6A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AssetsCurrentAbstract" xlink:label="loc_us-gaap_AssetsCurrentAbstract_E40E396A0B330BF22BC84CC03B82E543" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_3D4799439E7B678599744CC03B829D6A" xlink:to="loc_us-gaap_AssetsCurrentAbstract_E40E396A0B330BF22BC84CC03B82E543" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_DD0A552FE9D8B399EDD74CC03B8249CD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_E40E396A0B330BF22BC84CC03B82E543" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_DD0A552FE9D8B399EDD74CC03B8249CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_943EE7D263718B2B97594CC03B8319CF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_E40E396A0B330BF22BC84CC03B82E543" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsAtCarryingValue_943EE7D263718B2B97594CC03B8319CF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesCurrent" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesCurrent_CE6EF4AC449147E2FE9B4CC03B83E51C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_E40E396A0B330BF22BC84CC03B82E543" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesCurrent_CE6EF4AC449147E2FE9B4CC03B83E51C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsReceivableNetCurrent" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_E1F3CF272BB9FB9889D94CC03B833AF4" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_E40E396A0B330BF22BC84CC03B82E543" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_E1F3CF272BB9FB9889D94CC03B833AF4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_11808DF6FE23E9B516454CC03B839CAA" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_E40E396A0B330BF22BC84CC03B82E543" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_11808DF6FE23E9B516454CC03B839CAA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="loc_us-gaap_AssetsCurrent_3EEB2ED3824C8F04612B4CC03B83B650" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_E40E396A0B330BF22BC84CC03B82E543" xlink:to="loc_us-gaap_AssetsCurrent_3EEB2ED3824C8F04612B4CC03B83B650" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesNoncurrent" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesNoncurrent_70DB75AF47E2BCF5247E4CC03B830FEC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_3D4799439E7B678599744CC03B829D6A" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesNoncurrent_70DB75AF47E2BCF5247E4CC03B830FEC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_959861371F2F6D40C2714CC03B8371EA" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_3D4799439E7B678599744CC03B829D6A" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_959861371F2F6D40C2714CC03B8371EA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_F9412A1B6FEE1AB2B2DB4CC03B849C3A" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_3D4799439E7B678599744CC03B829D6A" xlink:to="loc_us-gaap_Goodwill_F9412A1B6FEE1AB2B2DB4CC03B849C3A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_8C79659A0A72564546D74CC03B8492DD" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_3D4799439E7B678599744CC03B829D6A" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_8C79659A0A72564546D74CC03B8492DD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DeferredTaxAssetsLiabilitiesNet" xlink:label="loc_us-gaap_DeferredTaxAssetsLiabilitiesNet_27F385B66DC2AAEBB1484CC03B8447CF" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_3D4799439E7B678599744CC03B829D6A" xlink:to="loc_us-gaap_DeferredTaxAssetsLiabilitiesNet_27F385B66DC2AAEBB1484CC03B8447CF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherAssetsNoncurrent" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_4CF5A196C74B19961C5C4CC03B84A03E" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_3D4799439E7B678599744CC03B829D6A" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_4CF5A196C74B19961C5C4CC03B84A03E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DueFromRelatedPartiesNoncurrent" xlink:label="loc_us-gaap_DueFromRelatedPartiesNoncurrent_DD30A6ABFE4CBF988D7C4CC03B84E546" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_3D4799439E7B678599744CC03B829D6A" xlink:to="loc_us-gaap_DueFromRelatedPartiesNoncurrent_DD30A6ABFE4CBF988D7C4CC03B84E546" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvestments" xlink:label="loc_us-gaap_EquityMethodInvestments_D3C1CFF9FD9FBC16F3F24CC03B8503C6" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_3D4799439E7B678599744CC03B829D6A" xlink:to="loc_us-gaap_EquityMethodInvestments_D3C1CFF9FD9FBC16F3F24CC03B8503C6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Assets" xlink:label="loc_us-gaap_Assets_BE73FB0F1D95F08E57F34CC03B859173" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_3D4799439E7B678599744CC03B829D6A" xlink:to="loc_us-gaap_Assets_BE73FB0F1D95F08E57F34CC03B859173" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9F97B4546696A41DFBB74CC03B85015C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_6BBD524801232A36CA5A4CC03B82C6B6" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9F97B4546696A41DFBB74CC03B85015C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_AD0FEE6518558621EC4D4CC03B85E02A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9F97B4546696A41DFBB74CC03B85015C" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_AD0FEE6518558621EC4D4CC03B85E02A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="loc_us-gaap_AccountsPayableCurrent_BF1BEBBA104700243FE44CC03B85AA11" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_AD0FEE6518558621EC4D4CC03B85E02A" xlink:to="loc_us-gaap_AccountsPayableCurrent_BF1BEBBA104700243FE44CC03B85AA11" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_D15349BB67A53C0E280E4CC03B868B42" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_AD0FEE6518558621EC4D4CC03B85E02A" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_D15349BB67A53C0E280E4CC03B868B42" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DeferredRevenueCurrent" xlink:label="loc_us-gaap_DeferredRevenueCurrent_2C9599DCE104325155264CC03B863587" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_AD0FEE6518558621EC4D4CC03B85E02A" xlink:to="loc_us-gaap_DeferredRevenueCurrent_2C9599DCE104325155264CC03B863587" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="loc_us-gaap_LiabilitiesCurrent_2BAC565A5D7812BA979F4CC03B86B513" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_AD0FEE6518558621EC4D4CC03B85E02A" xlink:to="loc_us-gaap_LiabilitiesCurrent_2BAC565A5D7812BA979F4CC03B86B513" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CapitalLeaseObligationsNoncurrent" xlink:label="loc_us-gaap_CapitalLeaseObligationsNoncurrent_8FABCD44D2CFD25653A64CC03B8614A2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9F97B4546696A41DFBB74CC03B85015C" xlink:to="loc_us-gaap_CapitalLeaseObligationsNoncurrent_8FABCD44D2CFD25653A64CC03B8614A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConvertibleLongTermNotesPayable" xlink:label="loc_us-gaap_ConvertibleLongTermNotesPayable_CA9A6915FBD2564C75954CC03B860393" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9F97B4546696A41DFBB74CC03B85015C" xlink:to="loc_us-gaap_ConvertibleLongTermNotesPayable_CA9A6915FBD2564C75954CC03B860393" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DeferredTaxLiabilities" xlink:label="loc_us-gaap_DeferredTaxLiabilities_2BA7C3669A1924E752434CC03B8636C8" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9F97B4546696A41DFBB74CC03B85015C" xlink:to="loc_us-gaap_DeferredTaxLiabilities_2BA7C3669A1924E752434CC03B8636C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DeferredRevenueNoncurrent" xlink:label="loc_us-gaap_DeferredRevenueNoncurrent_F3F80D33DAE650B2DA764CC03B8670A0" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9F97B4546696A41DFBB74CC03B85015C" xlink:to="loc_us-gaap_DeferredRevenueNoncurrent_F3F80D33DAE650B2DA764CC03B8670A0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_5EF4273722C6B75FCB4D4CC03B878E4C" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9F97B4546696A41DFBB74CC03B85015C" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_5EF4273722C6B75FCB4D4CC03B878E4C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount" xlink:label="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_96C99C567FF4AA7F74C84CC03B87C444" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_9F97B4546696A41DFBB74CC03B85015C" xlink:to="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_96C99C567FF4AA7F74C84CC03B87C444" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PreferredStockValue" xlink:label="loc_us-gaap_PreferredStockValue_AA0079AC7AAE53C664634CC03B87CB41" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_6BBD524801232A36CA5A4CC03B82C6B6" xlink:to="loc_us-gaap_PreferredStockValue_AA0079AC7AAE53C664634CC03B87CB41" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StockholdersEquityAbstract" xlink:label="loc_us-gaap_StockholdersEquityAbstract_AB458220126D13B7CF004CC03B8762DF" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_6BBD524801232A36CA5A4CC03B82C6B6" xlink:to="loc_us-gaap_StockholdersEquityAbstract_AB458220126D13B7CF004CC03B8762DF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CommonStockValue" xlink:label="loc_us-gaap_CommonStockValue_56C3AAEA528F8C1880114CC03B878A3E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_AB458220126D13B7CF004CC03B8762DF" xlink:to="loc_us-gaap_CommonStockValue_56C3AAEA528F8C1880114CC03B878A3E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TreasuryStockValue" xlink:label="loc_us-gaap_TreasuryStockValue_EBB71FA586801098217F4CC03B88CE0B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_AB458220126D13B7CF004CC03B8762DF" xlink:to="loc_us-gaap_TreasuryStockValue_EBB71FA586801098217F4CC03B88CE0B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AdditionalPaidInCapitalCommonStock" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_B2134D3796DB1BC4676B4CC03B88C4DE" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_AB458220126D13B7CF004CC03B8762DF" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_B2134D3796DB1BC4676B4CC03B88C4DE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_399FECD1DF6808F4F00B4CC03B889E23" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_AB458220126D13B7CF004CC03B8762DF" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_399FECD1DF6808F4F00B4CC03B889E23" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_D454EF087442C662AE574CC03B882C36" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_AB458220126D13B7CF004CC03B8762DF" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_D454EF087442C662AE574CC03B882C36" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="loc_us-gaap_StockholdersEquity_B428F4B7E360F46219744CC03B89927A" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_AB458220126D13B7CF004CC03B8762DF" xlink:to="loc_us-gaap_StockholdersEquity_B428F4B7E360F46219744CC03B89927A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_C458974C9D079BB936204CC03B898118" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityAbstract_AB458220126D13B7CF004CC03B8762DF" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_C458974C9D079BB936204CC03B898118" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationScheduleOfIncomeStatementEffectOfNewAccountingPronouncementsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems" xlink:label="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable" xlink:label="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable_141F316A2D61AAC445914CC03B67BBC2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable_141F316A2D61AAC445914CC03B67BBC2" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_58105B2EEC0898A880214CC03B683013" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable_141F316A2D61AAC445914CC03B67BBC2" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_58105B2EEC0898A880214CC03B683013" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_ECCF9FAB175D875EDC7A4CC03B687D51_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_58105B2EEC0898A880214CC03B683013" xlink:to="loc_us-gaap_TypeOfAdoptionMember_ECCF9FAB175D875EDC7A4CC03B687D51_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_ECCF9FAB175D875EDC7A4CC03B687D51" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_58105B2EEC0898A880214CC03B683013" xlink:to="loc_us-gaap_TypeOfAdoptionMember_ECCF9FAB175D875EDC7A4CC03B687D51" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccountingStandardsUpdate201409Member" xlink:label="loc_us-gaap_AccountingStandardsUpdate201409Member_F15FE3654F3D8DCFF8A44CC03B69EAAC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_ECCF9FAB175D875EDC7A4CC03B687D51" xlink:to="loc_us-gaap_AccountingStandardsUpdate201409Member_F15FE3654F3D8DCFF8A44CC03B69EAAC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_FAFFB1EB35623BE7422F4CC03B691DA8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionTable_141F316A2D61AAC445914CC03B67BBC2" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_FAFFB1EB35623BE7422F4CC03B691DA8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_1EB2501D5F9D0E7981CD4CC03B6994FB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_FAFFB1EB35623BE7422F4CC03B691DA8" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_1EB2501D5F9D0E7981CD4CC03B6994FB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain" xlink:label="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_1EB2501D5F9D0E7981CD4CC03B6994FB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionAxis_FAFFB1EB35623BE7422F4CC03B691DA8" xlink:to="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_1EB2501D5F9D0E7981CD4CC03B6994FB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member" xlink:label="loc_us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member_4FCFDDD0D0A387FA74814CC03B6AE33A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_1EB2501D5F9D0E7981CD4CC03B6994FB" xlink:to="loc_us-gaap_CalculatedUnderRevenueGuidanceInEffectBeforeTopic606Member_4FCFDDD0D0A387FA74814CC03B6AE33A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member" xlink:label="loc_us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member_8B4E5F8B9A75F02BD89C4CC03B6A8848" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_1EB2501D5F9D0E7981CD4CC03B6994FB" xlink:to="loc_us-gaap_DifferenceBetweenRevenueGuidanceInEffectBeforeAndAfterTopic606Member_8B4E5F8B9A75F02BD89C4CC03B6A8848" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_CalculatedunderRevenueGuidanceinEffectAfterTopic606Member" xlink:label="loc_sncr_CalculatedunderRevenueGuidanceinEffectAfterTopic606Member_28356B5E31AAF10036984CC03B6AF3DB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InitialApplicationPeriodCumulativeEffectTransitionDomain_1EB2501D5F9D0E7981CD4CC03B6994FB" xlink:to="loc_sncr_CalculatedunderRevenueGuidanceinEffectAfterTopic606Member_28356B5E31AAF10036984CC03B6AF3DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaap_Revenues_4F37F4CDD34A770AFCAC4CC03B6B1ECD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_Revenues_4F37F4CDD34A770AFCAC4CC03B6B1ECD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CostsAndExpensesAbstract" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_162AC6F0750E7FB2A4154CC03B6BFF86" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_162AC6F0750E7FB2A4154CC03B6BFF86" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CostOfServicesExcludingDepreciationDepletionAndAmortization" xlink:label="loc_us-gaap_CostOfServicesExcludingDepreciationDepletionAndAmortization_97BFAB886E9F647C1F854CC03B6BF0F5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_162AC6F0750E7FB2A4154CC03B6BFF86" xlink:to="loc_us-gaap_CostOfServicesExcludingDepreciationDepletionAndAmortization_97BFAB886E9F647C1F854CC03B6BF0F5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_A690F4DF57EF4E7E27984CC03B6C6D79" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_162AC6F0750E7FB2A4154CC03B6BFF86" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_A690F4DF57EF4E7E27984CC03B6C6D79" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpense" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_303080E64F6995D4D1C14CC03B6C4735" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_162AC6F0750E7FB2A4154CC03B6BFF86" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_303080E64F6995D4D1C14CC03B6C4735" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestructuringCharges" xlink:label="loc_us-gaap_RestructuringCharges_2ED6143B49891A1D14774CC03B6C6669" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_162AC6F0750E7FB2A4154CC03B6BFF86" xlink:to="loc_us-gaap_RestructuringCharges_2ED6143B49891A1D14774CC03B6C6669" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_7307B1AAC74F3A467C384CC03B6CBEFC" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_162AC6F0750E7FB2A4154CC03B6BFF86" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_7307B1AAC74F3A467C384CC03B6CBEFC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CostsAndExpenses" xlink:label="loc_us-gaap_CostsAndExpenses_8FB9BAB99CD91F41D27D4CC03B6CCC28" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_162AC6F0750E7FB2A4154CC03B6BFF86" xlink:to="loc_us-gaap_CostsAndExpenses_8FB9BAB99CD91F41D27D4CC03B6CCC28" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaap_OperatingIncomeLoss_C4A6521EDF5826165F8F4CC03B6D078B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_OperatingIncomeLoss_C4A6521EDF5826165F8F4CC03B6D078B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InvestmentIncomeInterest" xlink:label="loc_us-gaap_InvestmentIncomeInterest_C6349A2A438F6E855ABB4CC03B6E43E4" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_InvestmentIncomeInterest_C6349A2A438F6E855ABB4CC03B6E43E4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestExpense" xlink:label="loc_us-gaap_InterestExpense_7039F3AA8CB08497145E4CC03B6E547C" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_InterestExpense_7039F3AA8CB08497145E4CC03B6E547C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_4D5DDC702597584E06924CC03B6EE028" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_4D5DDC702597584E06924CC03B6EE028" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromEquityMethodInvestments" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_9B64225A6ECDC13CB1F04CC03B6FFFCD" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_9B64225A6ECDC13CB1F04CC03B6FFFCD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_CEFC2444EE8BE5341B6A4CC03B6F266B" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_CEFC2444EE8BE5341B6A4CC03B6F266B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_4DA29708E82B02EF00764CC03B6FD0E8" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_4DA29708E82B02EF00764CC03B6FD0E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_4FAC84987AC391876C9C4CC03B6F4D10" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_4FAC84987AC391876C9C4CC03B6F4D10" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_6214325CA1A1DEF290C94CC03B7017B4" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_6214325CA1A1DEF290C94CC03B7017B4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_4B89B16949DE2303A8B64CC03B702E3D" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_ProfitLoss_4B89B16949DE2303A8B64CC03B702E3D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_4B9C56EC46DAE533D8824CC03B70C25F" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_4B9C56EC46DAE533D8824CC03B70C25F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PreferredStockDividendsIncomeStatementImpact" xlink:label="loc_us-gaap_PreferredStockDividendsIncomeStatementImpact_E3868860F92EBAA8AEE94CCF51C4317D" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_PreferredStockDividendsIncomeStatementImpact_E3868860F92EBAA8AEE94CCF51C4317D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_509AB85079C73E8DD9A74CC03B7072A2" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_NetIncomeLoss_509AB85079C73E8DD9A74CC03B7072A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareBasicAbstract" xlink:label="loc_us-gaap_EarningsPerShareBasicAbstract_BFA1BF46112065F0F8664CC03B70A12E" xlink:type="locator" />
    <link:definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_EarningsPerShareBasicAbstract_BFA1BF46112065F0F8664CC03B70A12E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsPerBasicShare" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsPerBasicShare_2072C47D6A9F87A2CA8E4CC03B7039CA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_BFA1BF46112065F0F8664CC03B70A12E" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsPerBasicShare_2072C47D6A9F87A2CA8E4CC03B7039CA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare_B115B9E8ADBB80329E0F4CC03B7129D0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_BFA1BF46112065F0F8664CC03B70A12E" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare_B115B9E8ADBB80329E0F4CC03B7129D0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareBasic" xlink:label="loc_us-gaap_EarningsPerShareBasic_DFD630292494765F21994CC03B712020" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_BFA1BF46112065F0F8664CC03B70A12E" xlink:to="loc_us-gaap_EarningsPerShareBasic_DFD630292494765F21994CC03B712020" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareDilutedAbstract" xlink:label="loc_us-gaap_EarningsPerShareDilutedAbstract_6865713EE98769AE39AC4CC03B715C81" xlink:type="locator" />
    <link:definitionArc order="17" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_EarningsPerShareDilutedAbstract_6865713EE98769AE39AC4CC03B715C81" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare_C0C18BE6E75BFF9C68874CC03B71F944" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_6865713EE98769AE39AC4CC03B715C81" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare_C0C18BE6E75BFF9C68874CC03B71F944" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare_041E3A31ACA002E249C34CC03B72C1F8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_6865713EE98769AE39AC4CC03B715C81" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare_041E3A31ACA002E249C34CC03B72C1F8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="loc_us-gaap_EarningsPerShareDiluted_3E75D3B72AA31C48C81F4CC03B725216" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_6865713EE98769AE39AC4CC03B715C81" xlink:to="loc_us-gaap_EarningsPerShareDiluted_3E75D3B72AA31C48C81F4CC03B725216" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_F26A1E21869C6BF332034CC03B72BD8B" xlink:type="locator" />
    <link:definitionArc order="18" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueInitialApplicationPeriodCumulativeEffectTransitionLineItems_5EEBC6C0CC1893A812FB4CC03B6AFB71" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_F26A1E21869C6BF332034CC03B72BD8B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_A2D38B7C562229DA4EA54CC03B727D23" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_F26A1E21869C6BF332034CC03B72BD8B" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_A2D38B7C562229DA4EA54CC03B727D23" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_C4EA2A499617D2A110834CC03B7276A1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_F26A1E21869C6BF332034CC03B72BD8B" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_C4EA2A499617D2A110834CC03B7276A1" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/BasisOfPresentationAndConsolidationTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/CommitmentsAndContingencies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/CommitmentsAndContingenciesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingenciesLineItems" xlink:label="loc_us-gaap_LossContingenciesLineItems_6FBDB62600E785D10DF7F0B71D09AFCC" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingenciesTable" xlink:label="loc_us-gaap_LossContingenciesTable_BBE9BD7C548214E270B0F0B71D04B785" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_6FBDB62600E785D10DF7F0B71D09AFCC" xlink:to="loc_us-gaap_LossContingenciesTable_BBE9BD7C548214E270B0F0B71D04B785" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LitigationStatusAxis" xlink:label="loc_us-gaap_LitigationStatusAxis_F145B4DC35DB2FE425E3F0B71D045755" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_BBE9BD7C548214E270B0F0B71D04B785" xlink:to="loc_us-gaap_LitigationStatusAxis_F145B4DC35DB2FE425E3F0B71D045755" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LitigationStatusDomain" xlink:label="loc_us-gaap_LitigationStatusDomain_21BD84592E91426324BDF0B71D05B5F7_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LitigationStatusAxis_F145B4DC35DB2FE425E3F0B71D045755" xlink:to="loc_us-gaap_LitigationStatusDomain_21BD84592E91426324BDF0B71D05B5F7_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LitigationStatusDomain" xlink:label="loc_us-gaap_LitigationStatusDomain_21BD84592E91426324BDF0B71D05B5F7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LitigationStatusAxis_F145B4DC35DB2FE425E3F0B71D045755" xlink:to="loc_us-gaap_LitigationStatusDomain_21BD84592E91426324BDF0B71D05B5F7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PendingLitigationMember" xlink:label="loc_us-gaap_PendingLitigationMember_2979EBF6EF563F02B4F2F0B71D05E3A4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LitigationStatusDomain_21BD84592E91426324BDF0B71D05B5F7" xlink:to="loc_us-gaap_PendingLitigationMember_2979EBF6EF563F02B4F2F0B71D05E3A4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LitigationCaseAxis" xlink:label="loc_us-gaap_LitigationCaseAxis_AEF39E1BA9C54AECE579F0B71D05AA2D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_BBE9BD7C548214E270B0F0B71D04B785" xlink:to="loc_us-gaap_LitigationCaseAxis_AEF39E1BA9C54AECE579F0B71D05AA2D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LitigationCaseTypeDomain" xlink:label="loc_us-gaap_LitigationCaseTypeDomain_9B2651D1036D4D542100F0B71D053E8D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LitigationCaseAxis_AEF39E1BA9C54AECE579F0B71D05AA2D" xlink:to="loc_us-gaap_LitigationCaseTypeDomain_9B2651D1036D4D542100F0B71D053E8D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LitigationCaseTypeDomain" xlink:label="loc_us-gaap_LitigationCaseTypeDomain_9B2651D1036D4D542100F0B71D053E8D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LitigationCaseAxis_AEF39E1BA9C54AECE579F0B71D05AA2D" xlink:to="loc_us-gaap_LitigationCaseTypeDomain_9B2651D1036D4D542100F0B71D053E8D" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_TheSecuritiesLawActionsMember" xlink:label="loc_sncr_TheSecuritiesLawActionsMember_B42967C4038D20665DD7F0B71D06F21E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LitigationCaseTypeDomain_9B2651D1036D4D542100F0B71D053E8D" xlink:to="loc_sncr_TheSecuritiesLawActionsMember_B42967C4038D20665DD7F0B71D06F21E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationByTypeAxis" xlink:label="loc_us-gaap_ContingentConsiderationByTypeAxis_C926B0BE7A464DD85728F0B71D063F01" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_BBE9BD7C548214E270B0F0B71D04B785" xlink:to="loc_us-gaap_ContingentConsiderationByTypeAxis_C926B0BE7A464DD85728F0B71D063F01" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_83601158E8488B7A8460F0B71D07D809_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_C926B0BE7A464DD85728F0B71D063F01" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_83601158E8488B7A8460F0B71D07D809_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_83601158E8488B7A8460F0B71D07D809" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_C926B0BE7A464DD85728F0B71D063F01" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_83601158E8488B7A8460F0B71D07D809" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_ObligationsUnderAcquisitionAgreementMember" xlink:label="loc_sncr_ObligationsUnderAcquisitionAgreementMember_6D33A318BAEC0BE721ABF0B71D07F257" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_83601158E8488B7A8460F0B71D07D809" xlink:to="loc_sncr_ObligationsUnderAcquisitionAgreementMember_6D33A318BAEC0BE721ABF0B71D07F257" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_61B6BF2B09062C424211F0B71D08FC3F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_BBE9BD7C548214E270B0F0B71D04B785" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_61B6BF2B09062C424211F0B71D08FC3F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CE6763D99F52ACE75CADF0B71D0889C2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_61B6BF2B09062C424211F0B71D08FC3F" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CE6763D99F52ACE75CADF0B71D0889C2_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CE6763D99F52ACE75CADF0B71D0889C2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_61B6BF2B09062C424211F0B71D08FC3F" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CE6763D99F52ACE75CADF0B71D0889C2" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_MiyowaSAMember" xlink:label="loc_sncr_MiyowaSAMember_3B3BEDA918DFC49C5889F0B71D08417C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CE6763D99F52ACE75CADF0B71D0889C2" xlink:to="loc_sncr_MiyowaSAMember_3B3BEDA918DFC49C5889F0B71D08417C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingencyNewClaimsFiledNumber" xlink:label="loc_us-gaap_LossContingencyNewClaimsFiledNumber_CF58270B3DC9E71E258AF0B71D09CC5A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_6FBDB62600E785D10DF7F0B71D09AFCC" xlink:to="loc_us-gaap_LossContingencyNewClaimsFiledNumber_CF58270B3DC9E71E258AF0B71D09CC5A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LossContingencyNumberOfPlaintiffs" xlink:label="loc_us-gaap_LossContingencyNumberOfPlaintiffs_5C208358C5BA4270EC87F0B71D09D6A4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_6FBDB62600E785D10DF7F0B71D09AFCC" xlink:to="loc_us-gaap_LossContingencyNumberOfPlaintiffs_5C208358C5BA4270EC87F0B71D09D6A4" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/CondensedConsolidatedBalanceSheetsUnaudited" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/CondensedConsolidatedBalanceSheetsUnauditedParenthetical" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_F562BEB761B7F5D16FDC4CF44EF0E547" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_FFE4A67F97DA103CB4F84CF44EEFF0B6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_F562BEB761B7F5D16FDC4CF44EF0E547" xlink:to="loc_us-gaap_StatementTable_FFE4A67F97DA103CB4F84CF44EEFF0B6" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_20FE8BFA75B8071139F14CF44EEF7129" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_FFE4A67F97DA103CB4F84CF44EEFF0B6" xlink:to="loc_us-gaap_DebtInstrumentAxis_20FE8BFA75B8071139F14CF44EEF7129" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_C8F76874A89E83E052C04CF44EF080C1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_20FE8BFA75B8071139F14CF44EEF7129" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_C8F76874A89E83E052C04CF44EF080C1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_C8F76874A89E83E052C04CF44EF080C1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_20FE8BFA75B8071139F14CF44EEF7129" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_C8F76874A89E83E052C04CF44EF080C1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_27BFB47A87D31D2266824CF44EF074E9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_C8F76874A89E83E052C04CF44EF080C1" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_27BFB47A87D31D2266824CF44EF074E9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongTermDebtMember" xlink:label="loc_us-gaap_LongTermDebtMember_4BFBE23D9F33FB7D72994CF44EF05CEE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_C8F76874A89E83E052C04CF44EF080C1" xlink:to="loc_us-gaap_LongTermDebtMember_4BFBE23D9F33FB7D72994CF44EF05CEE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperationsAbstract" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperationsAbstract_35968BC00339C35154DA4CF44EF14148" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_F562BEB761B7F5D16FDC4CF44EF0E547" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperationsAbstract_35968BC00339C35154DA4CF44EF14148" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_C6FCD2A6FCD1EBABC1D04D0C88CA462A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperationsAbstract_35968BC00339C35154DA4CF44EF14148" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_C6FCD2A6FCD1EBABC1D04D0C88CA462A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_874EC81169E2D08EEB004D058F585291" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperationsAbstract_35968BC00339C35154DA4CF44EF14148" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_874EC81169E2D08EEB004D058F585291" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperationsAbstract_35968BC00339C35154DA4CF44EF14148" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_DepreciationDepletionandAmortizationNetofImpairment" xlink:label="loc_sncr_DepreciationDepletionandAmortizationNetofImpairment_0851F8A6B819C83039944CF44EF73B1D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:to="loc_sncr_DepreciationDepletionandAmortizationNetofImpairment_0851F8A6B819C83039944CF44EF73B1D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAdjustmentOfWarrants" xlink:label="loc_us-gaap_FairValueAdjustmentOfWarrants_86443DAB4174B4D79CBD4CF44EF744A1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:to="loc_us-gaap_FairValueAdjustmentOfWarrants_86443DAB4174B4D79CBD4CF44EF744A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AmortizationOfFinancingCosts" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_EB607FE5B701F4A7473A4CF44EF7A17B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_EB607FE5B701F4A7473A4CF44EF7A17B" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_PaidinKindInterestIncome" xlink:label="loc_sncr_PaidinKindInterestIncome_3AB64F6A05EE96071AD34CF44EF79DC7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:to="loc_sncr_PaidinKindInterestIncome_3AB64F6A05EE96071AD34CF44EF79DC7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions_188383D3866EC4B3CFB64CF44EF71135" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions_188383D3866EC4B3CFB64CF44EF71135" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GainLossOnDispositionOfAssets" xlink:label="loc_us-gaap_GainLossOnDispositionOfAssets_241163849C80E2E537D94CF44EF77CF5" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:to="loc_us-gaap_GainLossOnDispositionOfAssets_241163849C80E2E537D94CF44EF77CF5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal" xlink:label="loc_us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_AF1C97BCCEE85DB8A62D4CF44EF8FE3B" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:to="loc_us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_AF1C97BCCEE85DB8A62D4CF44EF8FE3B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AmortizationOfDebtDiscountPremium" xlink:label="loc_us-gaap_AmortizationOfDebtDiscountPremium_D53268D13AD9C67160054CF44EF89681" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:to="loc_us-gaap_AmortizationOfDebtDiscountPremium_D53268D13AD9C67160054CF44EF89681" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_EC1F6FD620D5BA3458324CF44EF8E8CE" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:to="loc_us-gaap_DeferredIncomeTaxExpenseBenefit_EC1F6FD620D5BA3458324CF44EF8E8CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestExpenseLesseeAssetsUnderCapitalLease" xlink:label="loc_us-gaap_InterestExpenseLesseeAssetsUnderCapitalLease_EA321481BC37937CF96C4CF44EF83504" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:to="loc_us-gaap_InterestExpenseLesseeAssetsUnderCapitalLease_EA321481BC37937CF96C4CF44EF83504" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:label="loc_us-gaap_ShareBasedCompensation_58F4D0707E0B3539A73A4CF44EF81700" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:to="loc_us-gaap_ShareBasedCompensation_58F4D0707E0B3539A73A4CF44EF81700" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_5285693B1EE0FCCDF9734CF44EF98A31" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_5285693B1EE0FCCDF9734CF44EF98A31" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_DD7DA9F1C78851B705D14CF44EF99D01" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_DD7DA9F1C78851B705D14CF44EF99D01" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_6B812511A2538C6C1C5D4CF44EF91F6E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_DD7DA9F1C78851B705D14CF44EF99D01" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_6B812511A2538C6C1C5D4CF44EF91F6E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_9368C4823BDAC3C13B234CF44EF9E97A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_DD7DA9F1C78851B705D14CF44EF99D01" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_9368C4823BDAC3C13B234CF44EF9E97A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_4724817A6DFB892B8F0B4CF44EFA4842" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_DD7DA9F1C78851B705D14CF44EF99D01" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_4724817A6DFB892B8F0B4CF44EFA4842" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayable" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_1D80297B967B7EFBB2464CF44EFA283B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_DD7DA9F1C78851B705D14CF44EF99D01" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_1D80297B967B7EFBB2464CF44EFA283B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilities" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_BB61109C365130AC82264CF44EFA06EF" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_DD7DA9F1C78851B705D14CF44EF99D01" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_BB61109C365130AC82264CF44EFA06EF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_FE21019ADD3F439988474CF44EFA4589" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_DD7DA9F1C78851B705D14CF44EF99D01" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_FE21019ADD3F439988474CF44EFA4589" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepaymentsOfDebtAndCapitalLeaseObligations" xlink:label="loc_us-gaap_RepaymentsOfDebtAndCapitalLeaseObligations_1B565FE8DC0D9E216A1E4CF44EFA558C" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_DD7DA9F1C78851B705D14CF44EF99D01" xlink:to="loc_us-gaap_RepaymentsOfDebtAndCapitalLeaseObligations_1B565FE8DC0D9E216A1E4CF44EFA558C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncreaseDecreaseInDeferredRevenue" xlink:label="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_20313C099D44C23414B84CF44EFA448E" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_DD7DA9F1C78851B705D14CF44EF99D01" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_20313C099D44C23414B84CF44EFA448E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_5789EF141A50CDF57F444CF44EFA8769" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_AB597D3D299694B1B55F4CF44EF698CD" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_5789EF141A50CDF57F444CF44EFA8769" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperationsAbstract" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperationsAbstract_B5E3B1F277E16D9991054CF44EFB7B66" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_F562BEB761B7F5D16FDC4CF44EF0E547" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperationsAbstract_B5E3B1F277E16D9991054CF44EFB7B66" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_ADCA6FF446DE46BB83C04CF44EFBA5A5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperationsAbstract_B5E3B1F277E16D9991054CF44EFB7B66" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_ADCA6FF446DE46BB83C04CF44EFBA5A5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsForSoftware" xlink:label="loc_us-gaap_PaymentsForSoftware_50DFA204FED6977387624CF44EFB501D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperationsAbstract_B5E3B1F277E16D9991054CF44EFB7B66" xlink:to="loc_us-gaap_PaymentsForSoftware_50DFA204FED6977387624CF44EFB501D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_C549A223F4491C0FC7704CF44EFB9280" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperationsAbstract_B5E3B1F277E16D9991054CF44EFB7B66" xlink:to="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_C549A223F4491C0FC7704CF44EFB9280" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireAvailableForSaleSecurities" xlink:label="loc_us-gaap_PaymentsToAcquireAvailableForSaleSecurities_FA2DDE221BCCBEF4A6914CF44EFC7C17" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperationsAbstract_B5E3B1F277E16D9991054CF44EFB7B66" xlink:to="loc_us-gaap_PaymentsToAcquireAvailableForSaleSecurities_FA2DDE221BCCBEF4A6914CF44EFC7C17" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities" xlink:label="loc_us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities_AF908E1F3009A33B4A264CF44EFCAB31" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperationsAbstract_B5E3B1F277E16D9991054CF44EFB7B66" xlink:to="loc_us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities_AF908E1F3009A33B4A264CF44EFCAB31" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireInterestInSubsidiariesAndAffiliates" xlink:label="loc_us-gaap_PaymentsToAcquireInterestInSubsidiariesAndAffiliates_03E46EFA2E3B93E8AC904CF44EFCB325" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperationsAbstract_B5E3B1F277E16D9991054CF44EFB7B66" xlink:to="loc_us-gaap_PaymentsToAcquireInterestInSubsidiariesAndAffiliates_03E46EFA2E3B93E8AC904CF44EFCB325" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_92160315AF5AED3C6DCF4CF44F01643C" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperationsAbstract_B5E3B1F277E16D9991054CF44EFB7B66" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_92160315AF5AED3C6DCF4CF44F01643C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_85E8BEBF0EF29716862B4CF44F021B9B" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperationsAbstract_B5E3B1F277E16D9991054CF44EFB7B66" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_85E8BEBF0EF29716862B4CF44F021B9B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperationsAbstract" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperationsAbstract_9E8D820E1BAA4214E4FD4CF44F02AE0F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_F562BEB761B7F5D16FDC4CF44EF0E547" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperationsAbstract_9E8D820E1BAA4214E4FD4CF44F02AE0F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromStockOptionsExercised" xlink:label="loc_us-gaap_ProceedsFromStockOptionsExercised_C39E6CE6F4AE8A8224874CF44F02A1C3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperationsAbstract_9E8D820E1BAA4214E4FD4CF44F02AE0F" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_C39E6CE6F4AE8A8224874CF44F02A1C3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsOfDebtIssuanceCosts" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_F9FEB3FE8AFD326F2DAA4CF44F025187" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperationsAbstract_9E8D820E1BAA4214E4FD4CF44F02AE0F" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_F9FEB3FE8AFD326F2DAA4CF44F025187" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_D6B43917FF3C339D4AF94CF44F02608F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperationsAbstract_9E8D820E1BAA4214E4FD4CF44F02AE0F" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_D6B43917FF3C339D4AF94CF44F02608F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepaymentsOfLinesOfCredit" xlink:label="loc_us-gaap_RepaymentsOfLinesOfCredit_9DB9D0B356C78EF4BC314CF44F037647" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperationsAbstract_9E8D820E1BAA4214E4FD4CF44F02AE0F" xlink:to="loc_us-gaap_RepaymentsOfLinesOfCredit_9DB9D0B356C78EF4BC314CF44F037647" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromSaleOfTreasuryStock" xlink:label="loc_us-gaap_ProceedsFromSaleOfTreasuryStock_58D73E8704B2DF61216A4CF44F030CF4" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperationsAbstract_9E8D820E1BAA4214E4FD4CF44F02AE0F" xlink:to="loc_us-gaap_ProceedsFromSaleOfTreasuryStock_58D73E8704B2DF61216A4CF44F030CF4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ProceedsFromIssuanceOfRedeemablePreferredStock" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfRedeemablePreferredStock_43F3AED768DD28AAE30A4CF44F039616" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperationsAbstract_9E8D820E1BAA4214E4FD4CF44F02AE0F" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfRedeemablePreferredStock_43F3AED768DD28AAE30A4CF44F039616" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepaymentsOfLongTermCapitalLeaseObligations" xlink:label="loc_us-gaap_RepaymentsOfLongTermCapitalLeaseObligations_F305DEE3306FBFB3B7B74CF44F03679D" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperationsAbstract_9E8D820E1BAA4214E4FD4CF44F02AE0F" xlink:to="loc_us-gaap_RepaymentsOfLongTermCapitalLeaseObligations_F305DEE3306FBFB3B7B74CF44F03679D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_18ADA396550F9313E10A4CF44F03E050" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperationsAbstract_9E8D820E1BAA4214E4FD4CF44F02AE0F" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_18ADA396550F9313E10A4CF44F03E050" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_AE3369A8E7CF2A43C5F04CF44F039BC8" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_F562BEB761B7F5D16FDC4CF44EF0E547" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_AE3369A8E7CF2A43C5F04CF44F039BC8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_D8DE4A389BDF6741899C4CF44F047E55" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_F562BEB761B7F5D16FDC4CF44EF0E547" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_D8DE4A389BDF6741899C4CF44F047E55" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_FF91288FD4D7F9BBF1ED4CF44F04D09A" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_F562BEB761B7F5D16FDC4CF44EF0E547" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_FF91288FD4D7F9BBF1ED4CF44F04D09A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SupplementalCashFlowInformationAbstract" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_A7568716733616A523794CF44F043827" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_F562BEB761B7F5D16FDC4CF44EF0E547" xlink:to="loc_us-gaap_SupplementalCashFlowInformationAbstract_A7568716733616A523794CF44F043827" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NoncashOrPartNoncashAcquisitionNoncashFinancialOrEquityInstrumentConsiderationSharesIssued1" xlink:label="loc_us-gaap_NoncashOrPartNoncashAcquisitionNoncashFinancialOrEquityInstrumentConsiderationSharesIssued1_AC3E4E9BA61E5BAE88794CF44F043F0F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_A7568716733616A523794CF44F043827" xlink:to="loc_us-gaap_NoncashOrPartNoncashAcquisitionNoncashFinancialOrEquityInstrumentConsiderationSharesIssued1_AC3E4E9BA61E5BAE88794CF44F043F0F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_608C508F24EEFBBF2F5F4CF44F050D78" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_A7568716733616A523794CF44F043827" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_608C508F24EEFBBF2F5F4CF44F050D78" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedCash" xlink:label="loc_us-gaap_RestrictedCash_530A6401CDAC534E56AC4CF44F05FD36" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_A7568716733616A523794CF44F043827" xlink:to="loc_us-gaap_RestrictedCash_530A6401CDAC534E56AC4CF44F05FD36" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/CondensedConsolidatedStatementsOfComprehensiveLossUnauditedStatement" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/CondensedConsolidatedStatementsOfOperationsUnaudited" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/Debt" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/DebtConvertibleSeniorNotesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_F4F2AAF1EA03089A1853421B7BA235FF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:to="loc_us-gaap_DebtInstrumentTable_F4F2AAF1EA03089A1853421B7BA235FF" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_71A5D1BECAA91F05A328421B7BA29B77" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_F4F2AAF1EA03089A1853421B7BA235FF" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_71A5D1BECAA91F05A328421B7BA29B77" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_F23A5D01CFB35B8CCB7E421B7BA20719_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_71A5D1BECAA91F05A328421B7BA29B77" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_F23A5D01CFB35B8CCB7E421B7BA20719_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_F23A5D01CFB35B8CCB7E421B7BA20719" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_71A5D1BECAA91F05A328421B7BA29B77" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_F23A5D01CFB35B8CCB7E421B7BA20719" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_ConvertibleSeniorNotesDue2019Member" xlink:label="loc_sncr_ConvertibleSeniorNotesDue2019Member_DD9F725D2DACFF95B6AF421B7BA28DDD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_F23A5D01CFB35B8CCB7E421B7BA20719" xlink:to="loc_sncr_ConvertibleSeniorNotesDue2019Member_DD9F725D2DACFF95B6AF421B7BA28DDD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_68F43824B56D12A552A7421B7BA3512B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_68F43824B56D12A552A7421B7BA3512B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_1BD26311931D3B29D681421B7BA3A915" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_1BD26311931D3B29D681421B7BA3A915" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_7792604CA4B93558AC9F421B7BA3FF7F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_7792604CA4B93558AC9F421B7BA3FF7F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DeferredFinanceCostsNoncurrentNet" xlink:label="loc_us-gaap_DeferredFinanceCostsNoncurrentNet_AC9853340B4DD53C10CA421B7BA3276C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:to="loc_us-gaap_DeferredFinanceCostsNoncurrentNet_AC9853340B4DD53C10CA421B7BA3276C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionRatio1" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_C342336D87E35A1052C7421B7BA401F3" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_C342336D87E35A1052C7421B7BA401F3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_F30261FCCBC88B0FB040421B7BA43BB9" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionPrice1_F30261FCCBC88B0FB040421B7BA43BB9" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_DebtInstrumentRepurchasePriceAsPercentageOfPrincipalAmountRepurchased" xlink:label="loc_sncr_DebtInstrumentRepurchasePriceAsPercentageOfPrincipalAmountRepurchased_1354CFC8F14F0810A85F421B7BA4A56E" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:to="loc_sncr_DebtInstrumentRepurchasePriceAsPercentageOfPrincipalAmountRepurchased_1354CFC8F14F0810A85F421B7BA4A56E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestExpenseDebt" xlink:label="loc_us-gaap_InterestExpenseDebt_3EEF163D989B8AD5F3DC421B7BA40532" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:to="loc_us-gaap_InterestExpenseDebt_3EEF163D989B8AD5F3DC421B7BA40532" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_F3614F46BA22F38AED60421B7BA594CE" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_F3614F46BA22F38AED60421B7BA594CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongTermDebtFairValue" xlink:label="loc_us-gaap_LongTermDebtFairValue_3D14DA09F25A8B775D9D421B7BA5541C" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:to="loc_us-gaap_LongTermDebtFairValue_3D14DA09F25A8B775D9D421B7BA5541C" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_ConvertibleDebtAdditionalInterestforNoncompliancePercent" xlink:label="loc_sncr_ConvertibleDebtAdditionalInterestforNoncompliancePercent_E0CC56D0EDF447E5C1F9421B7BA56E41" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:to="loc_sncr_ConvertibleDebtAdditionalInterestforNoncompliancePercent_E0CC56D0EDF447E5C1F9421B7BA56E41" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_ConvertibleDebtSecondAdditionalInterestforNoncompliancePercent" xlink:label="loc_sncr_ConvertibleDebtSecondAdditionalInterestforNoncompliancePercent_167D1692576151333748421B7BA541E2" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:to="loc_sncr_ConvertibleDebtSecondAdditionalInterestforNoncompliancePercent_167D1692576151333748421B7BA541E2" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_DebtInstrumentDebtDefaultPercentofHolders" xlink:label="loc_sncr_DebtInstrumentDebtDefaultPercentofHolders_D550070B9BB2C08C11A64230710C5A1F" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:to="loc_sncr_DebtInstrumentDebtDefaultPercentofHolders_D550070B9BB2C08C11A64230710C5A1F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue" xlink:label="loc_us-gaap_InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue_442ABE8A46F11B884FAA4230993433DC" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_65D10587FE69B4735653421B7BA3C81D" xlink:to="loc_us-gaap_InterestRateDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue_442ABE8A46F11B884FAA4230993433DC" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/DebtInterestExpenseDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_33F9711A96F9E36B9DC34BB2529C1A71" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_33780E0C4CD69718AB704BB252983448" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33F9711A96F9E36B9DC34BB2529C1A71" xlink:to="loc_us-gaap_DebtInstrumentTable_33780E0C4CD69718AB704BB252983448" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_47EE3587655388CC74794BB25298C098" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_33780E0C4CD69718AB704BB252983448" xlink:to="loc_us-gaap_DebtInstrumentAxis_47EE3587655388CC74794BB25298C098" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_BC397C9199674EBD0D834BB252984215_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_47EE3587655388CC74794BB25298C098" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_BC397C9199674EBD0D834BB252984215_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_BC397C9199674EBD0D834BB252984215" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_47EE3587655388CC74794BB25298C098" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_BC397C9199674EBD0D834BB252984215" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_AmendedAndRestatedCreditAgreementMember" xlink:label="loc_sncr_AmendedAndRestatedCreditAgreementMember_D93C0303C07ECF02A1794BB25299D287" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_BC397C9199674EBD0D834BB252984215" xlink:to="loc_sncr_AmendedAndRestatedCreditAgreementMember_D93C0303C07ECF02A1794BB25299D287" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_A65A8F565A7953832E284BB25299040B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_33780E0C4CD69718AB704BB252983448" xlink:to="loc_us-gaap_CreditFacilityAxis_A65A8F565A7953832E284BB25299040B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_7A9643B8ED0143A2F03B4BB25299A17C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_A65A8F565A7953832E284BB25299040B" xlink:to="loc_us-gaap_CreditFacilityDomain_7A9643B8ED0143A2F03B4BB25299A17C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_7A9643B8ED0143A2F03B4BB25299A17C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_A65A8F565A7953832E284BB25299040B" xlink:to="loc_us-gaap_CreditFacilityDomain_7A9643B8ED0143A2F03B4BB25299A17C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditMember" xlink:label="loc_us-gaap_LineOfCreditMember_CC76B6223229801293384BB2529AB868" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_7A9643B8ED0143A2F03B4BB25299A17C" xlink:to="loc_us-gaap_LineOfCreditMember_CC76B6223229801293384BB2529AB868" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SecuredDebtMember" xlink:label="loc_us-gaap_SecuredDebtMember_83BE37AFA0FFDE88A33F4BB2529A58C9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_7A9643B8ED0143A2F03B4BB25299A17C" xlink:to="loc_us-gaap_SecuredDebtMember_83BE37AFA0FFDE88A33F4BB2529A58C9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_63894CA9D684F81090334BB2529AB8F6" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_7A9643B8ED0143A2F03B4BB25299A17C" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_63894CA9D684F81090334BB2529AB8F6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityAxis" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_ED47456E38524D9C69EF4BB2529B07F7" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_33780E0C4CD69718AB704BB252983448" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_ED47456E38524D9C69EF4BB2529B07F7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_5D6867AEBACD51268AA74BB2529BFFF5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_ED47456E38524D9C69EF4BB2529B07F7" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_5D6867AEBACD51268AA74BB2529BFFF5_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_5D6867AEBACD51268AA74BB2529BFFF5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_ED47456E38524D9C69EF4BB2529B07F7" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_5D6867AEBACD51268AA74BB2529BFFF5" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_GoldmanSachsBankUSAMember" xlink:label="loc_sncr_GoldmanSachsBankUSAMember_E364F474E9C6D79248E04BB2529B3496" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_5D6867AEBACD51268AA74BB2529BFFF5" xlink:to="loc_sncr_GoldmanSachsBankUSAMember_E364F474E9C6D79248E04BB2529B3496" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_DC844CD203C8878980154BB2529B4A8D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_33780E0C4CD69718AB704BB252983448" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_DC844CD203C8878980154BB2529B4A8D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_B04BEE891535A4F95FB34BB2529CAE47_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_DC844CD203C8878980154BB2529B4A8D" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_B04BEE891535A4F95FB34BB2529CAE47_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_B04BEE891535A4F95FB34BB2529CAE47" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_DC844CD203C8878980154BB2529B4A8D" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_B04BEE891535A4F95FB34BB2529CAE47" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_ConvertibleSeniorNotesDue2019Member" xlink:label="loc_sncr_ConvertibleSeniorNotesDue2019Member_E700C1E8C1DD86487C8D4BB2529C1CC3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_B04BEE891535A4F95FB34BB2529CAE47" xlink:to="loc_sncr_ConvertibleSeniorNotesDue2019Member_E700C1E8C1DD86487C8D4BB2529C1CC3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AmortizationOfFinancingCosts" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_CE9FA2676A88CEBF735E4BB2529D2E69" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33F9711A96F9E36B9DC34BB2529C1A71" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_CE9FA2676A88CEBF735E4BB2529D2E69" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentUnusedBorrowingCapacityFee" xlink:label="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityFee_1BBC1925ED6258E024DB4BB2529D638D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33F9711A96F9E36B9DC34BB2529C1A71" xlink:to="loc_us-gaap_DebtInstrumentUnusedBorrowingCapacityFee_1BBC1925ED6258E024DB4BB2529D638D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestExpenseDebt" xlink:label="loc_us-gaap_InterestExpenseDebt_92D20820FAACCBF4D77A4BB2529D245C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33F9711A96F9E36B9DC34BB2529C1A71" xlink:to="loc_us-gaap_InterestExpenseDebt_92D20820FAACCBF4D77A4BB2529D245C" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_AdditionalInterestExpenseonDefault" xlink:label="loc_sncr_AdditionalInterestExpenseonDefault_37478B8C18EC4649942E4BB252A35C47" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33F9711A96F9E36B9DC34BB2529C1A71" xlink:to="loc_sncr_AdditionalInterestExpenseonDefault_37478B8C18EC4649942E4BB252A35C47" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestExpenseLesseeAssetsUnderCapitalLease" xlink:label="loc_us-gaap_InterestExpenseLesseeAssetsUnderCapitalLease_90CD862A1B2B3C9318674BB252A350F5" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33F9711A96F9E36B9DC34BB2529C1A71" xlink:to="loc_us-gaap_InterestExpenseLesseeAssetsUnderCapitalLease_90CD862A1B2B3C9318674BB252A350F5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestExpenseOther" xlink:label="loc_us-gaap_InterestExpenseOther_0D860847E608FCF5119E4BB252A3CF9A" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33F9711A96F9E36B9DC34BB2529C1A71" xlink:to="loc_us-gaap_InterestExpenseOther_0D860847E608FCF5119E4BB252A3CF9A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestExpense" xlink:label="loc_us-gaap_InterestExpense_8F795C0CE6FED6CE4DE74BB252A38B21" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_33F9711A96F9E36B9DC34BB2529C1A71" xlink:to="loc_us-gaap_InterestExpense_8F795C0CE6FED6CE4DE74BB252A38B21" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/DebtScheduleOfDebtDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_2265D3F5405B159467C74C5BF3F3C885" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_563C38BDBCF9BE136E804C5BF3F27386" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2265D3F5405B159467C74C5BF3F3C885" xlink:to="loc_us-gaap_DebtInstrumentTable_563C38BDBCF9BE136E804C5BF3F27386" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_A8CB026C778D804FFBDA4C5BF3F2BE5E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_563C38BDBCF9BE136E804C5BF3F27386" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_A8CB026C778D804FFBDA4C5BF3F2BE5E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_5CC580BE9DDFF460AD4B4C5BF3F342B9_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_A8CB026C778D804FFBDA4C5BF3F2BE5E" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_5CC580BE9DDFF460AD4B4C5BF3F342B9_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_5CC580BE9DDFF460AD4B4C5BF3F342B9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_A8CB026C778D804FFBDA4C5BF3F2BE5E" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_5CC580BE9DDFF460AD4B4C5BF3F342B9" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_ConvertibleSeniorNotesDue2019Member" xlink:label="loc_sncr_ConvertibleSeniorNotesDue2019Member_641D1FDE479F5593C1DC4C5BF3F3461E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_5CC580BE9DDFF460AD4B4C5BF3F342B9" xlink:to="loc_sncr_ConvertibleSeniorNotesDue2019Member_641D1FDE479F5593C1DC4C5BF3F3461E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_99ADADD74B12E409B2C14C5BF3F39670" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2265D3F5405B159467C74C5BF3F3C885" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_99ADADD74B12E409B2C14C5BF3F39670" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DeferredFinanceCostsNet" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_6EC6D1AB2F644CE703744C5BF3F4847D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2265D3F5405B159467C74C5BF3F3C885" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_6EC6D1AB2F644CE703744C5BF3F4847D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongTermDebtFairValue" xlink:label="loc_us-gaap_LongTermDebtFairValue_57F128399BD65FCF96424C5BF3F459B9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2265D3F5405B159467C74C5BF3F3C885" xlink:to="loc_us-gaap_LongTermDebtFairValue_57F128399BD65FCF96424C5BF3F459B9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShortTermBorrowings" xlink:label="loc_us-gaap_ShortTermBorrowings_925D17B64CACD0BAF33F4C5BF3F47447" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2265D3F5405B159467C74C5BF3F3C885" xlink:to="loc_us-gaap_ShortTermBorrowings_925D17B64CACD0BAF33F4C5BF3F47447" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongTermDebt" xlink:label="loc_us-gaap_LongTermDebt_FE7C8A0AA7D70E1229724C5BF3F45F23" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2265D3F5405B159467C74C5BF3F3C885" xlink:to="loc_us-gaap_LongTermDebt_FE7C8A0AA7D70E1229724C5BF3F45F23" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/DebtTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/DescriptionOfBusiness" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/DocumentAndEntityInformation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/EarningsPerCommonShare" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/EarningsPerCommonShareDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareBasicLineItems" xlink:label="loc_us-gaap_EarningsPerShareBasicLineItems_012E9A8C6D4932CC171A4D5792A7556A" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable" xlink:label="loc_us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable_F7C06C4ED61098EF05AC4D5792A51B3B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_012E9A8C6D4932CC171A4D5792A7556A" xlink:to="loc_us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable_F7C06C4ED61098EF05AC4D5792A51B3B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_76FCA4A3138618A072D04D5792A54B62" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable_F7C06C4ED61098EF05AC4D5792A51B3B" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_76FCA4A3138618A072D04D5792A54B62" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_C3561493277005BEDEDE4D5792A63B32_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_76FCA4A3138618A072D04D5792A54B62" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_C3561493277005BEDEDE4D5792A63B32_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_C3561493277005BEDEDE4D5792A63B32" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_76FCA4A3138618A072D04D5792A54B62" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_C3561493277005BEDEDE4D5792A63B32" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedStockMember" xlink:label="loc_us-gaap_RestrictedStockMember_B44A8D7EFB127C25A3E34D5792A6285B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_C3561493277005BEDEDE4D5792A63B32" xlink:to="loc_us-gaap_RestrictedStockMember_B44A8D7EFB127C25A3E34D5792A6285B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ConvertibleDebtSecuritiesMember" xlink:label="loc_us-gaap_ConvertibleDebtSecuritiesMember_E970E40FA1D9A1E073254D5792A6FAA9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_C3561493277005BEDEDE4D5792A63B32" xlink:to="loc_us-gaap_ConvertibleDebtSecuritiesMember_E970E40FA1D9A1E073254D5792A6FAA9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_238AD521FC542EA287C14D5792A6832E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_C3561493277005BEDEDE4D5792A63B32" xlink:to="loc_us-gaap_EmployeeStockOptionMember_238AD521FC542EA287C14D5792A6832E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SeriesAPreferredStockMember" xlink:label="loc_us-gaap_SeriesAPreferredStockMember_AEE912C8E729818382124D5792A6E2CA" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_C3561493277005BEDEDE4D5792A63B32" xlink:to="loc_us-gaap_SeriesAPreferredStockMember_AEE912C8E729818382124D5792A6E2CA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_9CB1EE2E1AEC034449034D5792A72B3E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable_F7C06C4ED61098EF05AC4D5792A51B3B" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_9CB1EE2E1AEC034449034D5792A72B3E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_AF892EA24D5F08E163164D5792A72C6C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_9CB1EE2E1AEC034449034D5792A72B3E" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_AF892EA24D5F08E163164D5792A72C6C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_AF892EA24D5F08E163164D5792A72C6C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_9CB1EE2E1AEC034449034D5792A72B3E" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_AF892EA24D5F08E163164D5792A72C6C" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_ConvertibleSeniorNotesDue2019Member" xlink:label="loc_sncr_ConvertibleSeniorNotesDue2019Member_346B78ED38E02ECF5EF04D5792A75462" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_AF892EA24D5F08E163164D5792A72C6C" xlink:to="loc_sncr_ConvertibleSeniorNotesDue2019Member_346B78ED38E02ECF5EF04D5792A75462" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareReconciliationAbstract" xlink:label="loc_us-gaap_EarningsPerShareReconciliationAbstract_620419253B4B2E9329614D5792A8CB03" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_012E9A8C6D4932CC171A4D5792A7556A" xlink:to="loc_us-gaap_EarningsPerShareReconciliationAbstract_620419253B4B2E9329614D5792A8CB03" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_87E5D0450BBE47C18FD94D5792A8752A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareReconciliationAbstract_620419253B4B2E9329614D5792A8CB03" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_87E5D0450BBE47C18FD94D5792A8752A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_547E6A414850D50DBA5F4D5792A88F05" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_87E5D0450BBE47C18FD94D5792A8752A" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsIncludingPortionAttributableToNoncontrollingInterest_547E6A414850D50DBA5F4D5792A88F05" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_8E0543DE42F4436407854D5792AAC2C8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_87E5D0450BBE47C18FD94D5792A8752A" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_8E0543DE42F4436407854D5792AAC2C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PreferredStockDividendsAndOtherAdjustments" xlink:label="loc_us-gaap_PreferredStockDividendsAndOtherAdjustments_3DE10C604F7F362AA7194D5792AB809D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_87E5D0450BBE47C18FD94D5792A8752A" xlink:to="loc_us-gaap_PreferredStockDividendsAndOtherAdjustments_3DE10C604F7F362AA7194D5792AB809D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromContinuingOperations" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperations_2123B32BD1AEA1A9F0EC4D5792AB3B44" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_87E5D0450BBE47C18FD94D5792A8752A" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperations_2123B32BD1AEA1A9F0EC4D5792AB3B44" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InterestOnConvertibleDebtNetOfTax" xlink:label="loc_us-gaap_InterestOnConvertibleDebtNetOfTax_7CF3623CA655ECE06BB04D5792AB1BEC" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_87E5D0450BBE47C18FD94D5792A8752A" xlink:to="loc_us-gaap_InterestOnConvertibleDebtNetOfTax_7CF3623CA655ECE06BB04D5792AB1BEC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLossFromContinuingOperationsAvailableToCommonShareholdersDiluted" xlink:label="loc_us-gaap_NetIncomeLossFromContinuingOperationsAvailableToCommonShareholdersDiluted_0D44415E34DEAA1B42424D5792ABE94E" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_87E5D0450BBE47C18FD94D5792A8752A" xlink:to="loc_us-gaap_NetIncomeLossFromContinuingOperationsAvailableToCommonShareholdersDiluted_0D44415E34DEAA1B42424D5792ABE94E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_F909E4600B68DC2CF4474D5792ABC3F2" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_87E5D0450BBE47C18FD94D5792A8752A" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_F909E4600B68DC2CF4474D5792ABC3F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_4AA16B92F9AEAEC933D84D5792ACF8D9" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDilutedAbstract_87E5D0450BBE47C18FD94D5792A8752A" xlink:to="loc_us-gaap_NetIncomeLoss_4AA16B92F9AEAEC933D84D5792ACF8D9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_60891BCB0098C65FB9BF4D5792B14B35" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareReconciliationAbstract_620419253B4B2E9329614D5792A8CB03" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_60891BCB0098C65FB9BF4D5792B14B35" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_97389E2E0E55B5943C804D5792B12732" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_60891BCB0098C65FB9BF4D5792B14B35" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_97389E2E0E55B5943C804D5792B12732" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract" xlink:label="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_809EEBBDCD3F53EC71E74D5792B287D0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_60891BCB0098C65FB9BF4D5792B14B35" xlink:to="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_809EEBBDCD3F53EC71E74D5792B287D0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities_66EF911FFBA1D7325B804D5792B26D8C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_809EEBBDCD3F53EC71E74D5792B287D0" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToConversionOfDebtSecurities_66EF911FFBA1D7325B804D5792B26D8C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_30015AB49850DF5B1EAE4D5792B2B2DD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_809EEBBDCD3F53EC71E74D5792B287D0" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_30015AB49850DF5B1EAE4D5792B2B2DD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_5F328D216D0EB072E5D24D5792B214C5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract_809EEBBDCD3F53EC71E74D5792B287D0" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_5F328D216D0EB072E5D24D5792B214C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareBasicAbstract" xlink:label="loc_us-gaap_EarningsPerShareBasicAbstract_27A7CD14733932814B154D5792B21288" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_012E9A8C6D4932CC171A4D5792A7556A" xlink:to="loc_us-gaap_EarningsPerShareBasicAbstract_27A7CD14733932814B154D5792B21288" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsPerBasicShare" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsPerBasicShare_25E21C3D1B976C6CF7FF4D5792B2A3A3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_27A7CD14733932814B154D5792B21288" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsPerBasicShare_25E21C3D1B976C6CF7FF4D5792B2A3A3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare_322707A70295AA18F3864D5792B35E83" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_27A7CD14733932814B154D5792B21288" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare_322707A70295AA18F3864D5792B35E83" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareBasic" xlink:label="loc_us-gaap_EarningsPerShareBasic_615E36ABD32DACF6E3614D5792B39807" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_27A7CD14733932814B154D5792B21288" xlink:to="loc_us-gaap_EarningsPerShareBasic_615E36ABD32DACF6E3614D5792B39807" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareDilutedAbstract" xlink:label="loc_us-gaap_EarningsPerShareDilutedAbstract_7AB9F9DF1A4B58ED0D494D5792B3E352" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_012E9A8C6D4932CC171A4D5792A7556A" xlink:to="loc_us-gaap_EarningsPerShareDilutedAbstract_7AB9F9DF1A4B58ED0D494D5792B3E352" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare_B45C3860CF23E413693E4D5792B3F799" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_7AB9F9DF1A4B58ED0D494D5792B3E352" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsPerDilutedShare_B45C3860CF23E413693E4D5792B3F799" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare_C4B58F39619792E2CABF4D5792B4D4CE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_7AB9F9DF1A4B58ED0D494D5792B3E352" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare_C4B58F39619792E2CABF4D5792B4D4CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="loc_us-gaap_EarningsPerShareDiluted_697992FCAFB33A1EE95B4D5792B4A409" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_7AB9F9DF1A4B58ED0D494D5792B3E352" xlink:to="loc_us-gaap_EarningsPerShareDiluted_697992FCAFB33A1EE95B4D5792B4A409" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_C7CBB48C18C075C5649B4D5792B4830B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_012E9A8C6D4932CC171A4D5792A7556A" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_C7CBB48C18C075C5649B4D5792B4830B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionRatio1" xlink:label="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_499EF4BC0C330B090BF14D5792B4DEAE" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicLineItems_012E9A8C6D4932CC171A4D5792A7556A" xlink:to="loc_us-gaap_DebtInstrumentConvertibleConversionRatio1_499EF4BC0C330B090BF14D5792B4DEAE" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/EarningsPerCommonShareTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/FairValueMeasurementsOfAssetsAndLiabilities" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/FairValueMeasurementsOfAssetsAndLiabilitiesAfsSecuritiesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_AE4A7977515D1FB44EC8421B7C0A9228" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_F2CB6236AFCE0173BEAB421B7C08B01B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_AE4A7977515D1FB44EC8421B7C0A9228" xlink:to="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_F2CB6236AFCE0173BEAB421B7C08B01B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashAndCashEquivalentsAxis" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_43816A53A0F113CB1E2C421B7C084A7C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_F2CB6236AFCE0173BEAB421B7C08B01B" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_43816A53A0F113CB1E2C421B7C084A7C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_6A0DCC6B4668A9B7E0C7421B7C08E5AC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_43816A53A0F113CB1E2C421B7C084A7C" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_6A0DCC6B4668A9B7E0C7421B7C08E5AC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_6A0DCC6B4668A9B7E0C7421B7C08E5AC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_43816A53A0F113CB1E2C421B7C084A7C" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_6A0DCC6B4668A9B7E0C7421B7C08E5AC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CertificatesOfDepositMember" xlink:label="loc_us-gaap_CertificatesOfDepositMember_26F90F233BF03E35C0AD421B7C096478" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_6A0DCC6B4668A9B7E0C7421B7C08E5AC" xlink:to="loc_us-gaap_CertificatesOfDepositMember_26F90F233BF03E35C0AD421B7C096478" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_D82492AF1DBDEB75215A421B7C09609B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_F2CB6236AFCE0173BEAB421B7C08B01B" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_D82492AF1DBDEB75215A421B7C09609B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_0F30CBCE437FBE3A8E51421B7C09543A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_D82492AF1DBDEB75215A421B7C09609B" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_0F30CBCE437FBE3A8E51421B7C09543A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_0F30CBCE437FBE3A8E51421B7C09543A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_D82492AF1DBDEB75215A421B7C09609B" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_0F30CBCE437FBE3A8E51421B7C09543A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MunicipalBondsMember" xlink:label="loc_us-gaap_MunicipalBondsMember_1D9BCA2414F2C3914BCB421B7C0A9A61" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_0F30CBCE437FBE3A8E51421B7C09543A" xlink:to="loc_us-gaap_MunicipalBondsMember_1D9BCA2414F2C3914BCB421B7C0A9A61" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesFairValueToAmortizedCostBasisAbstract" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesFairValueToAmortizedCostBasisAbstract_69AD5E934F673EAC69EF421B7C0AA40B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_AE4A7977515D1FB44EC8421B7C0A9228" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesFairValueToAmortizedCostBasisAbstract_69AD5E934F673EAC69EF421B7C0AA40B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAmortizedCost" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAmortizedCost_30E8CF04315D96D0467F421B7C0ACAEA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesFairValueToAmortizedCostBasisAbstract_69AD5E934F673EAC69EF421B7C0AA40B" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAmortizedCost_30E8CF04315D96D0467F421B7C0ACAEA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_CDAFBD61FEEF712C666F421B7C0A89C1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesFairValueToAmortizedCostBasisAbstract_69AD5E934F673EAC69EF421B7C0AA40B" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_CDAFBD61FEEF712C666F421B7C0A89C1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_69D92467A6C70966EBBA421B7C0B5B97" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesFairValueToAmortizedCostBasisAbstract_69AD5E934F673EAC69EF421B7C0AA40B" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_69D92467A6C70966EBBA421B7C0B5B97" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecurities_D5E94B7F52E7C72693EA421B7C0BB3DD" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesFairValueToAmortizedCostBasisAbstract_69AD5E934F673EAC69EF421B7C0AA40B" xlink:to="loc_us-gaap_AvailableForSaleSecurities_D5E94B7F52E7C72693EA421B7C0BB3DD" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/FairValueMeasurementsOfAssetsAndLiabilitiesAfsSecuritiesExpectedMaturitiesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/FairValueMeasurementsOfAssetsAndLiabilitiesAfsSecuritiesInUnrealizedLossPositionDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_2839CAA461E111AF4722421B7C026F83" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_50A514D65D5CC3E38E72421B7C00A97B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_2839CAA461E111AF4722421B7C026F83" xlink:to="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_50A514D65D5CC3E38E72421B7C00A97B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashAndCashEquivalentsAxis" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_EAEEF5F499F31FB9C5C8421B7C01A900" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_50A514D65D5CC3E38E72421B7C00A97B" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_EAEEF5F499F31FB9C5C8421B7C01A900" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_FD84266B52F14938AB7D421B7C0166CB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_EAEEF5F499F31FB9C5C8421B7C01A900" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_FD84266B52F14938AB7D421B7C0166CB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_FD84266B52F14938AB7D421B7C0166CB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_EAEEF5F499F31FB9C5C8421B7C01A900" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_FD84266B52F14938AB7D421B7C0166CB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CertificatesOfDepositMember" xlink:label="loc_us-gaap_CertificatesOfDepositMember_FE7C4DEE4478A3543D57421B7C01BFED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_FD84266B52F14938AB7D421B7C0166CB" xlink:to="loc_us-gaap_CertificatesOfDepositMember_FE7C4DEE4478A3543D57421B7C01BFED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_48C0B37FCDA9E0F009D3421B7C01154B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_50A514D65D5CC3E38E72421B7C00A97B" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_48C0B37FCDA9E0F009D3421B7C01154B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_5FF50D079E5B2796B773421B7C010A8C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_48C0B37FCDA9E0F009D3421B7C01154B" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_5FF50D079E5B2796B773421B7C010A8C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain" xlink:label="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_5FF50D079E5B2796B773421B7C010A8C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis_48C0B37FCDA9E0F009D3421B7C01154B" xlink:to="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_5FF50D079E5B2796B773421B7C010A8C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MunicipalBondsMember" xlink:label="loc_us-gaap_MunicipalBondsMember_BC74D176AC71945D48A8421B7C02F2B3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MajorTypesOfDebtAndEquitySecuritiesDomain_5FF50D079E5B2796B773421B7C010A8C" xlink:to="loc_us-gaap_MunicipalBondsMember_BC74D176AC71945D48A8421B7C02F2B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_5B951DC5F5E5E0CC9CD2421B7C0202F4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_2839CAA461E111AF4722421B7C026F83" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_5B951DC5F5E5E0CC9CD2421B7C0202F4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue_706AC18844A082591BD4421B7C03093A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract_5B951DC5F5E5E0CC9CD2421B7C0202F4" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue_706AC18844A082591BD4421B7C03093A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/FairValueMeasurementsOfAssetsAndLiabilitiesHierarchyDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A40E98E2D2BF2AD5A2721931E665491D" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_48F0C7C51AF3C55DD4E61931E66360EA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A40E98E2D2BF2AD5A2721931E665491D" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_48F0C7C51AF3C55DD4E61931E66360EA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_F61375654A5564AA7FB21931E664AC71" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_48F0C7C51AF3C55DD4E61931E66360EA" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_F61375654A5564AA7FB21931E664AC71" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9A6086374A721971C8051931E664CE01_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_F61375654A5564AA7FB21931E664AC71" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9A6086374A721971C8051931E664CE01_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9A6086374A721971C8051931E664CE01" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_F61375654A5564AA7FB21931E664AC71" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9A6086374A721971C8051931E664CE01" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_9DD074B0468A38CCAF3F1931E664F44D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9A6086374A721971C8051931E664CE01" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_9DD074B0468A38CCAF3F1931E664F44D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_7C20824FAAC9F5E9E4061931E6656E40" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9A6086374A721971C8051931E664CE01" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_7C20824FAAC9F5E9E4061931E6656E40" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_7F6ADB2B6B3FA1AE66A61931E665F54F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_9A6086374A721971C8051931E664CE01" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_7F6ADB2B6B3FA1AE66A61931E665F54F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AssetsFairValueDisclosureAbstract" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_55E9487E0ABB0F631B531931E66562D2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A40E98E2D2BF2AD5A2721931E665491D" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_55E9487E0ABB0F631B531931E66562D2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_898FAB3F9055C5FE90D61931E66563AA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_55E9487E0ABB0F631B531931E66562D2" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_898FAB3F9055C5FE90D61931E66563AA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesCurrent" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesCurrent_41AB35B982AADCC428291931E666C35D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_55E9487E0ABB0F631B531931E66562D2" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesCurrent_41AB35B982AADCC428291931E666C35D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AvailableForSaleSecuritiesNoncurrent" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesNoncurrent_4EB8B2466F7DF536B5751931E666D795" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_55E9487E0ABB0F631B531931E66562D2" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesNoncurrent_4EB8B2466F7DF536B5751931E666D795" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AssetsFairValueDisclosure" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_C6CEB6C6E8CD465F0D101931E666C795" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_55E9487E0ABB0F631B531931E66562D2" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_C6CEB6C6E8CD465F0D101931E666C795" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_5026D5C14735431B9BD81931E666702A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A40E98E2D2BF2AD5A2721931E665491D" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_5026D5C14735431B9BD81931E666702A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_8FCCF9E580800614294D1931E6679748" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_5026D5C14735431B9BD81931E666702A" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_8FCCF9E580800614294D1931E6679748" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_ConvertibleDebtInterestDerivative" xlink:label="loc_sncr_ConvertibleDebtInterestDerivative_110CD5010D8C1C6488A01931E667EFFB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_5026D5C14735431B9BD81931E666702A" xlink:to="loc_sncr_ConvertibleDebtInterestDerivative_110CD5010D8C1C6488A01931E667EFFB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_LiabilitiesFairValueDisclosure" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_79E128A5013FFDB6A48C1931E667B01A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_5026D5C14735431B9BD81931E666702A" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_79E128A5013FFDB6A48C1931E667B01A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisAlternativeAbstract" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisAlternativeAbstract_4787B55BF077371782521931E668AF39" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A40E98E2D2BF2AD5A2721931E665491D" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisAlternativeAbstract_4787B55BF077371782521931E668AF39" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RedeemableNoncontrollingInterestEquityOtherFairValue" xlink:label="loc_us-gaap_RedeemableNoncontrollingInterestEquityOtherFairValue_CF9D96C3AB4CE6768E661931E668EC98" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisAlternativeAbstract_4787B55BF077371782521931E668AF39" xlink:to="loc_us-gaap_RedeemableNoncontrollingInterestEquityOtherFairValue_CF9D96C3AB4CE6768E661931E668EC98" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueTransfersBetweenLevel1AndLevel2DescriptionAndPolicyAbstract" xlink:label="loc_us-gaap_FairValueTransfersBetweenLevel1AndLevel2DescriptionAndPolicyAbstract_0782ECCBC593E2DF2F8F1931E6681A02" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A40E98E2D2BF2AD5A2721931E665491D" xlink:to="loc_us-gaap_FairValueTransfersBetweenLevel1AndLevel2DescriptionAndPolicyAbstract_0782ECCBC593E2DF2F8F1931E6681A02" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_FairValueAssetsTransfersBetweenLevels12And3Amount" xlink:label="loc_sncr_FairValueAssetsTransfersBetweenLevels12And3Amount_D598E23F0B0E06CABB151931E6684CF1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueTransfersBetweenLevel1AndLevel2DescriptionAndPolicyAbstract_0782ECCBC593E2DF2F8F1931E6681A02" xlink:to="loc_sncr_FairValueAssetsTransfersBetweenLevels12And3Amount_D598E23F0B0E06CABB151931E6684CF1" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/FairValueMeasurementsOfAssetsAndLiabilitiesLevel3RedeemableNoncontrollingInterestsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_D1AB72E205CE44BEE0754870E0E3451C" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationTable_B884B0BEE4ABB1A63FB94870E0E1EB44" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_D1AB72E205CE44BEE0754870E0E3451C" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationTable_B884B0BEE4ABB1A63FB94870E0E1EB44" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_9C8E89BC20E45B75CCD34870E0E21251" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationTable_B884B0BEE4ABB1A63FB94870E0E1EB44" xlink:to="loc_dei_LegalEntityAxis_9C8E89BC20E45B75CCD34870E0E21251" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_274D74D83AABE68C04904870E0E22832_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_9C8E89BC20E45B75CCD34870E0E21251" xlink:to="loc_dei_EntityDomain_274D74D83AABE68C04904870E0E22832_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_274D74D83AABE68C04904870E0E22832" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_9C8E89BC20E45B75CCD34870E0E21251" xlink:to="loc_dei_EntityDomain_274D74D83AABE68C04904870E0E22832" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_RedeemableNoncontrollingInterestMember" xlink:label="loc_sncr_RedeemableNoncontrollingInterestMember_4C6D27433BC70DE801DD4870E0E23CDA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_274D74D83AABE68C04904870E0E22832" xlink:to="loc_sncr_RedeemableNoncontrollingInterestMember_4C6D27433BC70DE801DD4870E0E23CDA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_99BA23D797EC5BA4134F4870E0E38FFD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_D1AB72E205CE44BEE0754870E0E3451C" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_99BA23D797EC5BA4134F4870E0E38FFD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs_49136AF79E2F679818EC4870E0E360DA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_99BA23D797EC5BA4134F4870E0E38FFD" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs_49136AF79E2F679818EC4870E0E360DA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TemporaryEquityAccretionToRedemptionValue" xlink:label="loc_us-gaap_TemporaryEquityAccretionToRedemptionValue_C3AF0091D7100252BF474870E0E381D5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_99BA23D797EC5BA4134F4870E0E38FFD" xlink:to="loc_us-gaap_TemporaryEquityAccretionToRedemptionValue_C3AF0091D7100252BF474870E0E381D5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings_FFF0FC2C61B19BBC46F34870E0E467F5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationRollForward_99BA23D797EC5BA4134F4870E0E38FFD" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings_FFF0FC2C61B19BBC46F34870E0E467F5" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/FairValueMeasurementsOfAssetsAndLiabilitiesTables" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_9EDF60EA3D5BDD42E8F4421B7C1C3399" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_CF067007DEC743B3099D421B7C1A3228" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_9EDF60EA3D5BDD42E8F4421B7C1C3399" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_CF067007DEC743B3099D421B7C1A3228" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_F5B7B222CCE75E2C1884421B7C1A084D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_CF067007DEC743B3099D421B7C1A3228" xlink:to="loc_dei_LegalEntityAxis_F5B7B222CCE75E2C1884421B7C1A084D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_64E20C829EBA93B895D5421B7C1B9F41_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_F5B7B222CCE75E2C1884421B7C1A084D" xlink:to="loc_dei_EntityDomain_64E20C829EBA93B895D5421B7C1B9F41_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_64E20C829EBA93B895D5421B7C1B9F41" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_F5B7B222CCE75E2C1884421B7C1A084D" xlink:to="loc_dei_EntityDomain_64E20C829EBA93B895D5421B7C1B9F41" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_RedeemableNoncontrollingInterestMember" xlink:label="loc_sncr_RedeemableNoncontrollingInterestMember_C13C415BB247F3CF0CD5421B7C1B7847" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_64E20C829EBA93B895D5421B7C1B9F41" xlink:to="loc_sncr_RedeemableNoncontrollingInterestMember_C13C415BB247F3CF0CD5421B7C1B7847" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock" xlink:label="loc_us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_0D98A5A45346A2AF1F4D421B7C1CD89A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_9EDF60EA3D5BDD42E8F4421B7C1C3399" xlink:to="loc_us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_0D98A5A45346A2AF1F4D421B7C1CD89A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesReconciliationTableTextBlock" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesReconciliationTableTextBlock_866453E7CF41D1FC2876421B7C1C5BE8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_9EDF60EA3D5BDD42E8F4421B7C1C3399" xlink:to="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesReconciliationTableTextBlock_866453E7CF41D1FC2876421B7C1C5BE8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_InvestmentsClassifiedByContractualMaturityDateTableTextBlock" xlink:label="loc_us-gaap_InvestmentsClassifiedByContractualMaturityDateTableTextBlock_4C759B1A1BA79FD6629A421B7C1C87C8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_9EDF60EA3D5BDD42E8F4421B7C1C3399" xlink:to="loc_us-gaap_InvestmentsClassifiedByContractualMaturityDateTableTextBlock_4C759B1A1BA79FD6629A421B7C1C87C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock_5217CB31D6137C2F8890421B7C1DA1F4" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_9EDF60EA3D5BDD42E8F4421B7C1C3399" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock_5217CB31D6137C2F8890421B7C1DA1F4" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/IncomeTaxes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/IncomeTaxesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeTaxContingencyLineItems" xlink:label="loc_us-gaap_IncomeTaxContingencyLineItems_C530BD02EB198EB6CE0F4C5BF342ABDE" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeTaxContingencyTable" xlink:label="loc_us-gaap_IncomeTaxContingencyTable_A9B457EE5AF6DC25AD3F4C5BF3413641" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_C530BD02EB198EB6CE0F4C5BF342ABDE" xlink:to="loc_us-gaap_IncomeTaxContingencyTable_A9B457EE5AF6DC25AD3F4C5BF3413641" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_8094E8F40B23D28E4ECD4C5BF341BD9F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxContingencyTable_A9B457EE5AF6DC25AD3F4C5BF3413641" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_8094E8F40B23D28E4ECD4C5BF341BD9F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CF3FF21075CD70DE988D4C5BF34201CA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_8094E8F40B23D28E4ECD4C5BF341BD9F" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CF3FF21075CD70DE988D4C5BF34201CA_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CF3FF21075CD70DE988D4C5BF34201CA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_8094E8F40B23D28E4ECD4C5BF341BD9F" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CF3FF21075CD70DE988D4C5BF34201CA" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_AcquisitionofIntralinksCommonStockMember" xlink:label="loc_sncr_AcquisitionofIntralinksCommonStockMember_A850DDEAB08517F1953B4C5BF3428E0F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_CF3FF21075CD70DE988D4C5BF34201CA" xlink:to="loc_sncr_AcquisitionofIntralinksCommonStockMember_A850DDEAB08517F1953B4C5BF3428E0F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_F89EE7DDA9323703FF554C5BF342C3D1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_C530BD02EB198EB6CE0F4C5BF342ABDE" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_F89EE7DDA9323703FF554C5BF342C3D1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount" xlink:label="loc_us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount_ABCA9DEB775743850BAC4C5BF343825C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_C530BD02EB198EB6CE0F4C5BF342ABDE" xlink:to="loc_us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount_ABCA9DEB775743850BAC4C5BF343825C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromAcquisition" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromAcquisition_F6ECE07327E5DF09F37B4C5BF3434342" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxContingencyLineItems_C530BD02EB198EB6CE0F4C5BF342ABDE" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromAcquisition_F6ECE07327E5DF09F37B4C5BF3434342" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/Investments" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/InvestmentsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_B363347ACEC86CCA65804BB2539A2BA3" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8F0D61EC471D4D0EB6584BB2538EB709" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_B363347ACEC86CCA65804BB2539A2BA3" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8F0D61EC471D4D0EB6584BB2538EB709" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_693F2F7F7474B3FEEF2A4BB2538EFB9A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8F0D61EC471D4D0EB6584BB2538EB709" xlink:to="loc_dei_LegalEntityAxis_693F2F7F7474B3FEEF2A4BB2538EFB9A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_B3A3DD19EF872925F6494BB2538F9A36_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_693F2F7F7474B3FEEF2A4BB2538EFB9A" xlink:to="loc_dei_EntityDomain_B3A3DD19EF872925F6494BB2538F9A36_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_B3A3DD19EF872925F6494BB2538F9A36" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_693F2F7F7474B3FEEF2A4BB2538EFB9A" xlink:to="loc_dei_EntityDomain_B3A3DD19EF872925F6494BB2538F9A36" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_SequentialTechnologyInternationalHoldingsLLCMember" xlink:label="loc_sncr_SequentialTechnologyInternationalHoldingsLLCMember_03D7D12249BD677768B94BB2538F1CE5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_B3A3DD19EF872925F6494BB2538F9A36" xlink:to="loc_sncr_SequentialTechnologyInternationalHoldingsLLCMember_03D7D12249BD677768B94BB2538F1CE5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_CEB28B339F5F1B9B7EFC4BB25395FAB4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8F0D61EC471D4D0EB6584BB2538EB709" xlink:to="loc_us-gaap_CounterpartyNameAxis_CEB28B339F5F1B9B7EFC4BB25395FAB4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_11E2CE4137353C346C484BB253954F58_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_CEB28B339F5F1B9B7EFC4BB25395FAB4" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_11E2CE4137353C346C484BB253954F58_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_11E2CE4137353C346C484BB253954F58" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_CEB28B339F5F1B9B7EFC4BB25395FAB4" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_11E2CE4137353C346C484BB253954F58" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_GoldmanSachsBankUSAMember" xlink:label="loc_sncr_GoldmanSachsBankUSAMember_5160B28584424E3F0C5A4BB2539564EA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_11E2CE4137353C346C484BB253954F58" xlink:to="loc_sncr_GoldmanSachsBankUSAMember_5160B28584424E3F0C5A4BB2539564EA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsByNatureAxis" xlink:label="loc_us-gaap_GuaranteeObligationsByNatureAxis_A277731AE58211F28B374BB25395BCC1" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8F0D61EC471D4D0EB6584BB2538EB709" xlink:to="loc_us-gaap_GuaranteeObligationsByNatureAxis_A277731AE58211F28B374BB25395BCC1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_C67A151650EAA2731C124BB25396D198_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_A277731AE58211F28B374BB25395BCC1" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_C67A151650EAA2731C124BB25396D198_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_GuaranteeObligationsNatureDomain" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_C67A151650EAA2731C124BB25396D198" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_A277731AE58211F28B374BB25395BCC1" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_C67A151650EAA2731C124BB25396D198" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IndirectGuaranteeOfIndebtednessMember" xlink:label="loc_us-gaap_IndirectGuaranteeOfIndebtednessMember_2FEF81E5C50666E5204A4BB2539668CC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_C67A151650EAA2731C124BB25396D198" xlink:to="loc_us-gaap_IndirectGuaranteeOfIndebtednessMember_2FEF81E5C50666E5204A4BB2539668CC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisposalGroupClassificationAxis" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_E2CCB210301AB92F31914BB25396F342" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8F0D61EC471D4D0EB6584BB2538EB709" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_E2CCB210301AB92F31914BB25396F342" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisposalGroupClassificationDomain" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_519CAFCE464EEAB59A1F4BB253978D2A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_E2CCB210301AB92F31914BB25396F342" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_519CAFCE464EEAB59A1F4BB253978D2A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisposalGroupClassificationDomain" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_519CAFCE464EEAB59A1F4BB253978D2A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_E2CCB210301AB92F31914BB25396F342" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_519CAFCE464EEAB59A1F4BB253978D2A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DiscontinuedOperationsDisposedOfBySaleMember" xlink:label="loc_us-gaap_DiscontinuedOperationsDisposedOfBySaleMember_9541457AC357B4C1C3AA4BB25397A430" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_519CAFCE464EEAB59A1F4BB253978D2A" xlink:to="loc_us-gaap_DiscontinuedOperationsDisposedOfBySaleMember_9541457AC357B4C1C3AA4BB25397A430" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9AA31B3EC2FBCECFEC764BB25397B36F" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8F0D61EC471D4D0EB6584BB2538EB709" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9AA31B3EC2FBCECFEC764BB25397B36F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_5B88AD137C56303694074BB2539771AE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9AA31B3EC2FBCECFEC764BB25397B36F" xlink:to="loc_us-gaap_RelatedPartyDomain_5B88AD137C56303694074BB2539771AE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_5B88AD137C56303694074BB2539771AE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9AA31B3EC2FBCECFEC764BB25397B36F" xlink:to="loc_us-gaap_RelatedPartyDomain_5B88AD137C56303694074BB2539771AE" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_STIHMember" xlink:label="loc_sncr_STIHMember_49FC4B62D64F06C8D38B4BB25398C1A2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_5B88AD137C56303694074BB2539771AE" xlink:to="loc_sncr_STIHMember_49FC4B62D64F06C8D38B4BB25398C1A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_4E11A4E6EBAF66741A714BB25398029A" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8F0D61EC471D4D0EB6584BB2538EB709" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_4E11A4E6EBAF66741A714BB25398029A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeNameDomain" xlink:label="loc_us-gaap_EquityMethodInvesteeNameDomain_4D1E4739A274B18D91764BB2539888FB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_4E11A4E6EBAF66741A714BB25398029A" xlink:to="loc_us-gaap_EquityMethodInvesteeNameDomain_4D1E4739A274B18D91764BB2539888FB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeNameDomain" xlink:label="loc_us-gaap_EquityMethodInvesteeNameDomain_4D1E4739A274B18D91764BB2539888FB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_4E11A4E6EBAF66741A714BB25398029A" xlink:to="loc_us-gaap_EquityMethodInvesteeNameDomain_4D1E4739A274B18D91764BB2539888FB" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_SequentialTechnologyInternationalLLCMember" xlink:label="loc_sncr_SequentialTechnologyInternationalLLCMember_FCE3C1674E5878E2A70E4BB25398E113" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvesteeNameDomain_4D1E4739A274B18D91764BB2539888FB" xlink:to="loc_sncr_SequentialTechnologyInternationalLLCMember_FCE3C1674E5878E2A70E4BB25398E113" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_806B9571C14CAAEAD9EE4BB25399B684" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8F0D61EC471D4D0EB6584BB2538EB709" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_806B9571C14CAAEAD9EE4BB25399B684" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_1C1F043531969304E0DC4BB25399867A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_806B9571C14CAAEAD9EE4BB25399B684" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_1C1F043531969304E0DC4BB25399867A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_1C1F043531969304E0DC4BB25399867A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_806B9571C14CAAEAD9EE4BB25399B684" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_1C1F043531969304E0DC4BB25399867A" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_BPODivestitureMember" xlink:label="loc_sncr_BPODivestitureMember_47BD02B18F7B4D9D03EF4BB253992D72" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_1C1F043531969304E0DC4BB25399867A" xlink:to="loc_sncr_BPODivestitureMember_47BD02B18F7B4D9D03EF4BB253992D72" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" xlink:label="loc_us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis_3BAFA7D4181FD8C85F5C4BB2539A96CF" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_8F0D61EC471D4D0EB6584BB2538EB709" xlink:to="loc_us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis_3BAFA7D4181FD8C85F5C4BB2539A96CF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ClassificationOfVariableInterestEntityDomain" xlink:label="loc_us-gaap_ClassificationOfVariableInterestEntityDomain_F84B913F6F1EDD7FA45F4BB2539AC3E0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis_3BAFA7D4181FD8C85F5C4BB2539A96CF" xlink:to="loc_us-gaap_ClassificationOfVariableInterestEntityDomain_F84B913F6F1EDD7FA45F4BB2539AC3E0_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ClassificationOfVariableInterestEntityDomain" xlink:label="loc_us-gaap_ClassificationOfVariableInterestEntityDomain_F84B913F6F1EDD7FA45F4BB2539AC3E0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis_3BAFA7D4181FD8C85F5C4BB2539A96CF" xlink:to="loc_us-gaap_ClassificationOfVariableInterestEntityDomain_F84B913F6F1EDD7FA45F4BB2539AC3E0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_BB68CAFD06F46882CB654BB2539A415C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassificationOfVariableInterestEntityDomain_F84B913F6F1EDD7FA45F4BB2539AC3E0" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_BB68CAFD06F46882CB654BB2539A415C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvestments" xlink:label="loc_us-gaap_EquityMethodInvestments_34A99D99C1DE2E889AA64BB2539A6E43" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_B363347ACEC86CCA65804BB2539A2BA3" xlink:to="loc_us-gaap_EquityMethodInvestments_34A99D99C1DE2E889AA64BB2539A6E43" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_B8B5D565B136C54E044D4BB2539B922B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_B363347ACEC86CCA65804BB2539A2BA3" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_B8B5D565B136C54E044D4BB2539B922B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeLossFromEquityMethodInvestments" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_4EE667A5EE783A5A09B54BB2539BED82" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_B363347ACEC86CCA65804BB2539A2BA3" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_4EE667A5EE783A5A09B54BB2539BED82" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_DurationofCustomerContract" xlink:label="loc_sncr_DurationofCustomerContract_24E634EEA2C8D30E32D34BB2539B0475" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_B363347ACEC86CCA65804BB2539A2BA3" xlink:to="loc_sncr_DurationofCustomerContract_24E634EEA2C8D30E32D34BB2539B0475" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_DiscontinuedOperationIntraEntityAmountsDiscontinuedOperationAfterDisposalRevenue" xlink:label="loc_us-gaap_DiscontinuedOperationIntraEntityAmountsDiscontinuedOperationAfterDisposalRevenue_FBB1AD275711E2F7B9984BB2539BA3ED" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_B363347ACEC86CCA65804BB2539A2BA3" xlink:to="loc_us-gaap_DiscontinuedOperationIntraEntityAmountsDiscontinuedOperationAfterDisposalRevenue_FBB1AD275711E2F7B9984BB2539BA3ED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedCashCurrent" xlink:label="loc_us-gaap_RestrictedCashCurrent_0343675FA697D4A4C5FA4BB2539C5D79" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_B363347ACEC86CCA65804BB2539A2BA3" xlink:to="loc_us-gaap_RestrictedCashCurrent_0343675FA697D4A4C5FA4BB2539C5D79" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/InvestmentsEquityMethodInvestmentDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_26E459B7640EF3B1586BDC77B1D281AF" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_DF2D6568B269853C509CDC77B1CD8FDE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_26E459B7640EF3B1586BDC77B1D281AF" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_DF2D6568B269853C509CDC77B1CD8FDE" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_4375878FC5EB327081E2DC77DC696CF2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_DF2D6568B269853C509CDC77B1CD8FDE" xlink:to="loc_us-gaap_CounterpartyNameAxis_4375878FC5EB327081E2DC77DC696CF2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_C56CF29677BBEA615415DC77DC6A22C4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_4375878FC5EB327081E2DC77DC696CF2" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_C56CF29677BBEA615415DC77DC6A22C4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_C56CF29677BBEA615415DC77DC6A22C4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_4375878FC5EB327081E2DC77DC696CF2" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_C56CF29677BBEA615415DC77DC6A22C4" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_STIMember" xlink:label="loc_sncr_STIMember_F6916332955894997E70DC77FB4F0A8D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_C56CF29677BBEA615415DC77DC6A22C4" xlink:to="loc_sncr_STIMember_F6916332955894997E70DC77FB4F0A8D" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_EquityMethodInvestmentSummarizedFinancialInformationRestrictedCashandCashEquivalentsCurrent" xlink:label="loc_sncr_EquityMethodInvestmentSummarizedFinancialInformationRestrictedCashandCashEquivalentsCurrent_FE10D081B36B81D43BC1DC6A49197B7B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_26E459B7640EF3B1586BDC77B1D281AF" xlink:to="loc_sncr_EquityMethodInvestmentSummarizedFinancialInformationRestrictedCashandCashEquivalentsCurrent_FE10D081B36B81D43BC1DC6A49197B7B" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_EquityMethodInvestmentSummarizedFinancialInformationAccountsReceivableNetCurrent" xlink:label="loc_sncr_EquityMethodInvestmentSummarizedFinancialInformationAccountsReceivableNetCurrent_5AC16D1AC78112823E9EDC6A4919A771" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_26E459B7640EF3B1586BDC77B1D281AF" xlink:to="loc_sncr_EquityMethodInvestmentSummarizedFinancialInformationAccountsReceivableNetCurrent_5AC16D1AC78112823E9EDC6A4919A771" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvestmentSummarizedFinancialInformationAssets" xlink:label="loc_us-gaap_EquityMethodInvestmentSummarizedFinancialInformationAssets_08D71AD81354147A3CCADC6A4919340F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_26E459B7640EF3B1586BDC77B1D281AF" xlink:to="loc_us-gaap_EquityMethodInvestmentSummarizedFinancialInformationAssets_08D71AD81354147A3CCADC6A4919340F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvestmentSummarizedFinancialInformationCurrentLiabilities" xlink:label="loc_us-gaap_EquityMethodInvestmentSummarizedFinancialInformationCurrentLiabilities_8DFCCE89A5C31DA4948ADC6A4919A7BD" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_26E459B7640EF3B1586BDC77B1D281AF" xlink:to="loc_us-gaap_EquityMethodInvestmentSummarizedFinancialInformationCurrentLiabilities_8DFCCE89A5C31DA4948ADC6A4919A7BD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvestmentSummarizedFinancialInformationLiabilities" xlink:label="loc_us-gaap_EquityMethodInvestmentSummarizedFinancialInformationLiabilities_3C8F06E88E4917DCECEADC6A491AC36F" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_26E459B7640EF3B1586BDC77B1D281AF" xlink:to="loc_us-gaap_EquityMethodInvestmentSummarizedFinancialInformationLiabilities_3C8F06E88E4917DCECEADC6A491AC36F" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/InvestmentsNoteReceivableDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsLineItems" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_0F1FFDD81162068A4F82421B7BD9DBE0" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentsTable" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_B273FE89D2C8029BF81B421B7BD73DDB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_0F1FFDD81162068A4F82421B7BD9DBE0" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_B273FE89D2C8029BF81B421B7BD73DDB" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis" xlink:label="loc_us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis_31C4BF9E9A2A370445DE421B7BD7DFF2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_B273FE89D2C8029BF81B421B7BD73DDB" xlink:to="loc_us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis_31C4BF9E9A2A370445DE421B7BD7DFF2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ClassificationOfVariableInterestEntityDomain" xlink:label="loc_us-gaap_ClassificationOfVariableInterestEntityDomain_5F75B66F505EFE88A6F4421B7BD81A4A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis_31C4BF9E9A2A370445DE421B7BD7DFF2" xlink:to="loc_us-gaap_ClassificationOfVariableInterestEntityDomain_5F75B66F505EFE88A6F4421B7BD81A4A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ClassificationOfVariableInterestEntityDomain" xlink:label="loc_us-gaap_ClassificationOfVariableInterestEntityDomain_5F75B66F505EFE88A6F4421B7BD81A4A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis_31C4BF9E9A2A370445DE421B7BD7DFF2" xlink:to="loc_us-gaap_ClassificationOfVariableInterestEntityDomain_5F75B66F505EFE88A6F4421B7BD81A4A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_VariableInterestEntityPrimaryBeneficiaryMember" xlink:label="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_D58EFDF9D28DFFDD3232421B7BD8DA02" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassificationOfVariableInterestEntityDomain_5F75B66F505EFE88A6F4421B7BD81A4A" xlink:to="loc_us-gaap_VariableInterestEntityPrimaryBeneficiaryMember_D58EFDF9D28DFFDD3232421B7BD8DA02" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis" xlink:label="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_BC20F5077A94CD521A19421B7BD81CA0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsTable_B273FE89D2C8029BF81B421B7BD73DDB" xlink:to="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_BC20F5077A94CD521A19421B7BD81CA0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeNameDomain" xlink:label="loc_us-gaap_EquityMethodInvesteeNameDomain_752B4EC78A56440A2687421B7BD86B65_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_BC20F5077A94CD521A19421B7BD81CA0" xlink:to="loc_us-gaap_EquityMethodInvesteeNameDomain_752B4EC78A56440A2687421B7BD86B65_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityMethodInvesteeNameDomain" xlink:label="loc_us-gaap_EquityMethodInvesteeNameDomain_752B4EC78A56440A2687421B7BD86B65" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_BC20F5077A94CD521A19421B7BD81CA0" xlink:to="loc_us-gaap_EquityMethodInvesteeNameDomain_752B4EC78A56440A2687421B7BD86B65" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_SequentialTechnologyInternationalLLCMember" xlink:label="loc_sncr_SequentialTechnologyInternationalLLCMember_BE3352A5C58189A4F670421B7BD947C1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvesteeNameDomain_752B4EC78A56440A2687421B7BD86B65" xlink:to="loc_sncr_SequentialTechnologyInternationalLLCMember_BE3352A5C58189A4F670421B7BD947C1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NotesReceivableGross" xlink:label="loc_us-gaap_NotesReceivableGross_5CE7DCB31BFA234FAE53421B7BD90728" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_0F1FFDD81162068A4F82421B7BD9DBE0" xlink:to="loc_us-gaap_NotesReceivableGross_5CE7DCB31BFA234FAE53421B7BD90728" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ImpairedFinancingReceivableRecordedInvestment" xlink:label="loc_us-gaap_ImpairedFinancingReceivableRecordedInvestment_50633BBCFB2064D9592B421B7BD9AB7A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_0F1FFDD81162068A4F82421B7BD9DBE0" xlink:to="loc_us-gaap_ImpairedFinancingReceivableRecordedInvestment_50633BBCFB2064D9592B421B7BD9AB7A" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_FinancingReceivableUnamortizedDiscountPremiumCumulativeBalance" xlink:label="loc_sncr_FinancingReceivableUnamortizedDiscountPremiumCumulativeBalance_2D95E77401CC1DADC7CC421B7BDA2FF2" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_0F1FFDD81162068A4F82421B7BD9DBE0" xlink:to="loc_sncr_FinancingReceivableUnamortizedDiscountPremiumCumulativeBalance_2D95E77401CC1DADC7CC421B7BDA2FF2" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_FinancingReceivableUnamortizedDiscountPremium" xlink:label="loc_sncr_FinancingReceivableUnamortizedDiscountPremium_9DFDE58B477E23699641421B7BDAB2F2" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_0F1FFDD81162068A4F82421B7BD9DBE0" xlink:to="loc_sncr_FinancingReceivableUnamortizedDiscountPremium_9DFDE58B477E23699641421B7BDAB2F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccruedInvestmentIncomeReceivable" xlink:label="loc_us-gaap_AccruedInvestmentIncomeReceivable_476C72B84CD07DEB9552421B7BDA2B50" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_0F1FFDD81162068A4F82421B7BD9DBE0" xlink:to="loc_us-gaap_AccruedInvestmentIncomeReceivable_476C72B84CD07DEB9552421B7BDA2B50" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedCashCurrent" xlink:label="loc_us-gaap_RestrictedCashCurrent_D2C1C106A30D7C544D23422203347F84" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_0F1FFDD81162068A4F82421B7BD9DBE0" xlink:to="loc_us-gaap_RestrictedCashCurrent_D2C1C106A30D7C544D23422203347F84" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_AccruedInvestmentIncomeReceivableNet" xlink:label="loc_sncr_AccruedInvestmentIncomeReceivableNet_F34E7625374664404CDE421B7BDA91A9" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_0F1FFDD81162068A4F82421B7BD9DBE0" xlink:to="loc_sncr_AccruedInvestmentIncomeReceivableNet_F34E7625374664404CDE421B7BDA91A9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EscrowDeposit" xlink:label="loc_us-gaap_EscrowDeposit_DFEDD33ABD26F69E4093421B7BDA5FE4" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_0F1FFDD81162068A4F82421B7BD9DBE0" xlink:to="loc_us-gaap_EscrowDeposit_DFEDD33ABD26F69E4093421B7BDA5FE4" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_InterestonEscrowDeposit" xlink:label="loc_sncr_InterestonEscrowDeposit_5EA29DF66E880F030AFC421B7BDA2780" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_0F1FFDD81162068A4F82421B7BD9DBE0" xlink:to="loc_sncr_InterestonEscrowDeposit_5EA29DF66E880F030AFC421B7BDA2780" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_InterestonEscrowDepositNet" xlink:label="loc_sncr_InterestonEscrowDepositNet_12962F1825768ED1C68D421B7BDBF4A4" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_0F1FFDD81162068A4F82421B7BD9DBE0" xlink:to="loc_sncr_InterestonEscrowDepositNet_12962F1825768ED1C68D421B7BDBF4A4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_NotesReceivableNet" xlink:label="loc_us-gaap_NotesReceivableNet_46E8EDA1B75ECD59F186421B7BDB8CDE" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_0F1FFDD81162068A4F82421B7BD9DBE0" xlink:to="loc_us-gaap_NotesReceivableNet_46E8EDA1B75ECD59F186421B7BDB8CDE" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_FinancingReceivableNetCumulativeBalance" xlink:label="loc_sncr_FinancingReceivableNetCumulativeBalance_45ABDA956E094801CFB1421B7BDB2E93" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfEquityMethodInvestmentsLineItems_0F1FFDD81162068A4F82421B7BD9DBE0" xlink:to="loc_sncr_FinancingReceivableNetCumulativeBalance_45ABDA956E094801CFB1421B7BDB2E93" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/InvestmentsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/Restructuring" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/RestructuringDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestructuringCostAndReserveLineItems" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_CCF088BB6402709EAA1D28A55B3DC875" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_A63361A0407104B9313428A55B3A80CF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_CCF088BB6402709EAA1D28A55B3DC875" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_A63361A0407104B9313428A55B3A80CF" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestructuringCostAndReserveAxis" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_FFF6D2D1C0BE8DA6D63028A55B3BDCCD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_A63361A0407104B9313428A55B3A80CF" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_FFF6D2D1C0BE8DA6D63028A55B3BDCCD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TypeOfRestructuringDomain" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_943D0F8A9F963627F0FB28A55B3BFB39_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_FFF6D2D1C0BE8DA6D63028A55B3BDCCD" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_943D0F8A9F963627F0FB28A55B3BFB39_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TypeOfRestructuringDomain" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_943D0F8A9F963627F0FB28A55B3BFB39" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_FFF6D2D1C0BE8DA6D63028A55B3BDCCD" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_943D0F8A9F963627F0FB28A55B3BFB39" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeSeveranceMember" xlink:label="loc_us-gaap_EmployeeSeveranceMember_5BCE875103E5E71A9A9C28A55B3B840E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_943D0F8A9F963627F0FB28A55B3BFB39" xlink:to="loc_us-gaap_EmployeeSeveranceMember_5BCE875103E5E71A9A9C28A55B3B840E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_FacilityClosingMember" xlink:label="loc_us-gaap_FacilityClosingMember_7945C04DC714311CF84F28A55B3C5950" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_943D0F8A9F963627F0FB28A55B3BFB39" xlink:to="loc_us-gaap_FacilityClosingMember_7945C04DC714311CF84F28A55B3C5950" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_546CBD2599CEDAA8472828A55B3CFE47" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_A63361A0407104B9313428A55B3A80CF" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_546CBD2599CEDAA8472828A55B3CFE47" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_06D97502AF2A29B9306328A55B3C2C88_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_546CBD2599CEDAA8472828A55B3CFE47" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_06D97502AF2A29B9306328A55B3C2C88_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_06D97502AF2A29B9306328A55B3C2C88" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_546CBD2599CEDAA8472828A55B3CFE47" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_06D97502AF2A29B9306328A55B3C2C88" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AccruedLiabilitiesMember" xlink:label="loc_us-gaap_AccruedLiabilitiesMember_F585013F65B7EBE9DA7628A55B3C91DD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_06D97502AF2A29B9306328A55B3C2C88" xlink:to="loc_us-gaap_AccruedLiabilitiesMember_F585013F65B7EBE9DA7628A55B3C91DD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestructuringReserveRollForward" xlink:label="loc_us-gaap_RestructuringReserveRollForward_3972113D62919758CDB528A55B3D3C30" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_CCF088BB6402709EAA1D28A55B3DC875" xlink:to="loc_us-gaap_RestructuringReserveRollForward_3972113D62919758CDB528A55B3D3C30" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestructuringReserve" xlink:label="loc_us-gaap_RestructuringReserve_A030032AD020D31E622728A55B3DFED9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_3972113D62919758CDB528A55B3D3C30" xlink:to="loc_us-gaap_RestructuringReserve_A030032AD020D31E622728A55B3DFED9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestructuringCharges" xlink:label="loc_us-gaap_RestructuringCharges_570F14CFA7771D3D621A28A55B3D85E2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_3972113D62919758CDB528A55B3D3C30" xlink:to="loc_us-gaap_RestructuringCharges_570F14CFA7771D3D621A28A55B3D85E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsForRestructuring" xlink:label="loc_us-gaap_PaymentsForRestructuring_591C81B8D5FEE7E7996528A55B3DD2E4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringReserveRollForward_3972113D62919758CDB528A55B3D3C30" xlink:to="loc_us-gaap_PaymentsForRestructuring_591C81B8D5FEE7E7996528A55B3DD2E4" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/RestructuringTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/StockholdersEquity" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/StockholdersEquityBlackScholesAssumptionsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_D33252FAAC5502A2575EF0B71D6FFF9D" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3812F98AF719ABBB2327F0B71D6E76AD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_D33252FAAC5502A2575EF0B71D6FFF9D" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3812F98AF719ABBB2327F0B71D6E76AD" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_8F1D29A12D14E9686A0CF0B71D6ED6D9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3812F98AF719ABBB2327F0B71D6E76AD" xlink:to="loc_us-gaap_AwardTypeAxis_8F1D29A12D14E9686A0CF0B71D6ED6D9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_CF37102B01690C6F47DCF0B71D6FE8A3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_8F1D29A12D14E9686A0CF0B71D6ED6D9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_CF37102B01690C6F47DCF0B71D6FE8A3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_CF37102B01690C6F47DCF0B71D6FE8A3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_8F1D29A12D14E9686A0CF0B71D6ED6D9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_CF37102B01690C6F47DCF0B71D6FE8A3" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_EmployeeAndDirectorsStockOptionsMember" xlink:label="loc_sncr_EmployeeAndDirectorsStockOptionsMember_E5898657D13ECF34C31CF0B71D6FFCA6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_CF37102B01690C6F47DCF0B71D6FE8A3" xlink:to="loc_sncr_EmployeeAndDirectorsStockOptionsMember_E5898657D13ECF34C31CF0B71D6FFCA6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_1E6D430CA240B14AF385F0B71D6F155E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_D33252FAAC5502A2575EF0B71D6FFF9D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_1E6D430CA240B14AF385F0B71D6F155E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_A1B0176BC12A8650C040F0B71D70A84E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_1E6D430CA240B14AF385F0B71D6F155E" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_A1B0176BC12A8650C040F0B71D70A84E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_2AEA40E2E10D4FD28257F0B71D7016E3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_1E6D430CA240B14AF385F0B71D6F155E" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_2AEA40E2E10D4FD28257F0B71D7016E3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_BBD2F50E7EB3FD4A99F7F0B71D7077F7" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_1E6D430CA240B14AF385F0B71D6F155E" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_BBD2F50E7EB3FD4A99F7F0B71D7077F7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_A32C860FD06DE589BD5FF0B71D70B3F6" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_1E6D430CA240B14AF385F0B71D6F155E" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_A32C860FD06DE589BD5FF0B71D70B3F6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7E907E7FCF2C7D305477F0B71D70A823" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract_1E6D430CA240B14AF385F0B71D6F155E" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7E907E7FCF2C7D305477F0B71D70A823" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/StockholdersEquityEsppAndOtherDisclosuresDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_24FFBBCF4BA6B619338D284CF64746F0" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_D2A46FE94CD1D99506D6284CF646BC6B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_24FFBBCF4BA6B619338D284CF64746F0" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_D2A46FE94CD1D99506D6284CF646BC6B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_752120B528199D4ED37D284CF6465BA7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_D2A46FE94CD1D99506D6284CF646BC6B" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_752120B528199D4ED37D284CF6465BA7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_C4DBAC3FF4AFD1C1483F284CF646C1CF_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_752120B528199D4ED37D284CF6465BA7" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_C4DBAC3FF4AFD1C1483F284CF646C1CF_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_C4DBAC3FF4AFD1C1483F284CF646C1CF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_752120B528199D4ED37D284CF6465BA7" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_C4DBAC3FF4AFD1C1483F284CF646C1CF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeStockMember" xlink:label="loc_us-gaap_EmployeeStockMember_2B17090E587D09F3D11E284CF647D52A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_C4DBAC3FF4AFD1C1483F284CF646C1CF" xlink:to="loc_us-gaap_EmployeeStockMember_2B17090E587D09F3D11E284CF647D52A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract_0AD89F69C42605FF1DFE284CF6478A42" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_24FFBBCF4BA6B619338D284CF64746F0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract_0AD89F69C42605FF1DFE284CF6478A42" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_TermOfEmployeeStockPurchasePlan" xlink:label="loc_sncr_TermOfEmployeeStockPurchasePlan_A3190C727757F17AA93C284CF6476F57" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract_0AD89F69C42605FF1DFE284CF6478A42" xlink:to="loc_sncr_TermOfEmployeeStockPurchasePlan_A3190C727757F17AA93C284CF6476F57" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_436A543E9320646155CC284CF6488CB7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract_0AD89F69C42605FF1DFE284CF6478A42" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_436A543E9320646155CC284CF6488CB7" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_EmployeeStockPurchasePlanPayrollWithholdingPeriod" xlink:label="loc_sncr_EmployeeStockPurchasePlanPayrollWithholdingPeriod_2040B3F35EA3EB4D787F284CF648D67C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract_0AD89F69C42605FF1DFE284CF6478A42" xlink:to="loc_sncr_EmployeeStockPurchasePlanPayrollWithholdingPeriod_2040B3F35EA3EB4D787F284CF648D67C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_48D39E460A1A96EE8EA1284CF64829BE" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract_0AD89F69C42605FF1DFE284CF6478A42" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_48D39E460A1A96EE8EA1284CF64829BE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum_1E1FE4AC68FE812F8735284CF648BDEE" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract_0AD89F69C42605FF1DFE284CF6478A42" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum_1E1FE4AC68FE812F8735284CF648BDEE" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_CommonStockMaximumNumberofSharesAuthorizedWithinanyPurchasePeriod" xlink:label="loc_sncr_CommonStockMaximumNumberofSharesAuthorizedWithinanyPurchasePeriod_445EEAB1C5AD891B9BAB284CF648921E" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract_0AD89F69C42605FF1DFE284CF6478A42" xlink:to="loc_sncr_CommonStockMaximumNumberofSharesAuthorizedWithinanyPurchasePeriod_445EEAB1C5AD891B9BAB284CF648921E" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_CommonStockMaximumValueofSharesAuthorizedWithinanyCalendarYear" xlink:label="loc_sncr_CommonStockMaximumValueofSharesAuthorizedWithinanyCalendarYear_3D8F56BB2D28DC91CDC9284CF648E33A" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract_0AD89F69C42605FF1DFE284CF6478A42" xlink:to="loc_sncr_CommonStockMaximumValueofSharesAuthorizedWithinanyCalendarYear_3D8F56BB2D28DC91CDC9284CF648E33A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/StockholdersEquityNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ClassOfStockLineItems" xlink:label="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_DADB7B8BF678F90B2F614CACABEEFFDF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_DADB7B8BF678F90B2F614CACABEEFFDF" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_F6A12EC476485C07761E4CACABEE1EF5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_DADB7B8BF678F90B2F614CACABEEFFDF" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_F6A12EC476485C07761E4CACABEE1EF5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_89889D9A9AAD788A7C734CACABEFE0D8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_F6A12EC476485C07761E4CACABEE1EF5" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_89889D9A9AAD788A7C734CACABEFE0D8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_89889D9A9AAD788A7C734CACABEFE0D8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_F6A12EC476485C07761E4CACABEE1EF5" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_89889D9A9AAD788A7C734CACABEFE0D8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_60D0B721C07266F44C274CACABEF565E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_89889D9A9AAD788A7C734CACABEFE0D8" xlink:to="loc_us-gaap_SubsequentEventMember_60D0B721C07266F44C274CACABEF565E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TitleOfIndividualAxis" xlink:label="loc_us-gaap_TitleOfIndividualAxis_CCF3184FCFE0A0277F4C4CACABEF9B06" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_DADB7B8BF678F90B2F614CACABEEFFDF" xlink:to="loc_us-gaap_TitleOfIndividualAxis_CCF3184FCFE0A0277F4C4CACABEF9B06" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_93CE448819E8CF0A8C324CACABEF9975_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TitleOfIndividualAxis_CCF3184FCFE0A0277F4C4CACABEF9B06" xlink:to="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_93CE448819E8CF0A8C324CACABEF9975_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_93CE448819E8CF0A8C324CACABEF9975" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TitleOfIndividualAxis_CCF3184FCFE0A0277F4C4CACABEF9B06" xlink:to="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_93CE448819E8CF0A8C324CACABEF9975" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ChiefExecutiveOfficerMember" xlink:label="loc_us-gaap_ChiefExecutiveOfficerMember_AD1B2FA340079D6657B44CACABF0F754" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_93CE448819E8CF0A8C324CACABEF9975" xlink:to="loc_us-gaap_ChiefExecutiveOfficerMember_AD1B2FA340079D6657B44CACABF0F754" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BoardOfDirectorsChairmanMember" xlink:label="loc_us-gaap_BoardOfDirectorsChairmanMember_8080E39541340B47253A4CACABF09F5E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_93CE448819E8CF0A8C324CACABEF9975" xlink:to="loc_us-gaap_BoardOfDirectorsChairmanMember_8080E39541340B47253A4CACABF09F5E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementScenarioAxis" xlink:label="loc_us-gaap_StatementScenarioAxis_AE37A6F3031E81DF3FE14CACABF0C3E8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_DADB7B8BF678F90B2F614CACABEEFFDF" xlink:to="loc_us-gaap_StatementScenarioAxis_AE37A6F3031E81DF3FE14CACABF0C3E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="loc_us-gaap_ScenarioUnspecifiedDomain_9AA78547357C1FB2121E4CACABF0B551_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementScenarioAxis_AE37A6F3031E81DF3FE14CACABF0C3E8" xlink:to="loc_us-gaap_ScenarioUnspecifiedDomain_9AA78547357C1FB2121E4CACABF0B551_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="loc_us-gaap_ScenarioUnspecifiedDomain_9AA78547357C1FB2121E4CACABF0B551" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementScenarioAxis_AE37A6F3031E81DF3FE14CACABF0C3E8" xlink:to="loc_us-gaap_ScenarioUnspecifiedDomain_9AA78547357C1FB2121E4CACABF0B551" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_EBITDANonComplianceMember" xlink:label="loc_sncr_EBITDANonComplianceMember_182B980E3AD18EC46A564CACABF15C7C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScenarioUnspecifiedDomain_9AA78547357C1FB2121E4CACABF0B551" xlink:to="loc_sncr_EBITDANonComplianceMember_182B980E3AD18EC46A564CACABF15C7C" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_ConversionofStockMember" xlink:label="loc_sncr_ConversionofStockMember_CE6F9DA5B1EE54A22AF24CACABF1AA7B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScenarioUnspecifiedDomain_9AA78547357C1FB2121E4CACABF0B551" xlink:to="loc_sncr_ConversionofStockMember_CE6F9DA5B1EE54A22AF24CACABF1AA7B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_B98681CAD2FECEE6E16D4CACABF128A4" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_DADB7B8BF678F90B2F614CACABEEFFDF" xlink:to="loc_us-gaap_CounterpartyNameAxis_B98681CAD2FECEE6E16D4CACABF128A4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_BD01BD908E75FF75DF8C4CACABF17806_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_B98681CAD2FECEE6E16D4CACABF128A4" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_BD01BD908E75FF75DF8C4CACABF17806_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_BD01BD908E75FF75DF8C4CACABF17806" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_B98681CAD2FECEE6E16D4CACABF128A4" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_BD01BD908E75FF75DF8C4CACABF17806" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_SilverPrivateHoldingsILLCMember" xlink:label="loc_sncr_SilverPrivateHoldingsILLCMember_35750BA18A2FEF9A86794CACABF2960B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_BD01BD908E75FF75DF8C4CACABF17806" xlink:to="loc_sncr_SilverPrivateHoldingsILLCMember_35750BA18A2FEF9A86794CACABF2960B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_3D2238F0B49132E532E44CACABF20748" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_DADB7B8BF678F90B2F614CACABEEFFDF" xlink:to="loc_us-gaap_RangeAxis_3D2238F0B49132E532E44CACABF20748" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_B9630183A988E65E48014CACABF2E9EE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_3D2238F0B49132E532E44CACABF20748" xlink:to="loc_us-gaap_RangeMember_B9630183A988E65E48014CACABF2E9EE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_B9630183A988E65E48014CACABF2E9EE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_3D2238F0B49132E532E44CACABF20748" xlink:to="loc_us-gaap_RangeMember_B9630183A988E65E48014CACABF2E9EE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_DC68D8B195D81CDA08334CACABF30B9E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_B9630183A988E65E48014CACABF2E9EE" xlink:to="loc_us-gaap_MinimumMember_DC68D8B195D81CDA08334CACABF30B9E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_1DACA64B66C77ED2C97A4CACABF35D90" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_B9630183A988E65E48014CACABF2E9EE" xlink:to="loc_us-gaap_MaximumMember_1DACA64B66C77ED2C97A4CACABF35D90" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_OwnershipPercentageAxis" xlink:label="loc_sncr_OwnershipPercentageAxis_7714F78C6DDC045B980F4CACABF39E12" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_DADB7B8BF678F90B2F614CACABEEFFDF" xlink:to="loc_sncr_OwnershipPercentageAxis_7714F78C6DDC045B980F4CACABF39E12" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_OwnershipPercentageDomain" xlink:label="loc_sncr_OwnershipPercentageDomain_D41D46F0CA0E85A02B764CACABF3D04C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_sncr_OwnershipPercentageAxis_7714F78C6DDC045B980F4CACABF39E12" xlink:to="loc_sncr_OwnershipPercentageDomain_D41D46F0CA0E85A02B764CACABF3D04C_default" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_OwnershipPercentageDomain" xlink:label="loc_sncr_OwnershipPercentageDomain_D41D46F0CA0E85A02B764CACABF3D04C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_sncr_OwnershipPercentageAxis_7714F78C6DDC045B980F4CACABF39E12" xlink:to="loc_sncr_OwnershipPercentageDomain_D41D46F0CA0E85A02B764CACABF3D04C" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_TenPercentorGreaterOwnershipMember" xlink:label="loc_sncr_TenPercentorGreaterOwnershipMember_28D0519015EA79A5D28D4CACABF3D3CB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sncr_OwnershipPercentageDomain_D41D46F0CA0E85A02B764CACABF3D04C" xlink:to="loc_sncr_TenPercentorGreaterOwnershipMember_28D0519015EA79A5D28D4CACABF3D3CB" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_GreaterthanFiveandLessthanTenPercentOwnershipMember" xlink:label="loc_sncr_GreaterthanFiveandLessthanTenPercentOwnershipMember_04A9144F48456FAEB3044CACABF4BB35" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_sncr_OwnershipPercentageDomain_D41D46F0CA0E85A02B764CACABF3D04C" xlink:to="loc_sncr_GreaterthanFiveandLessthanTenPercentOwnershipMember_04A9144F48456FAEB3044CACABF4BB35" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_6BDFDB925C2484B31F774CACABF49191" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_DADB7B8BF678F90B2F614CACABEEFFDF" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_6BDFDB925C2484B31F774CACABF49191" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ABF21065C1EA6EC9DDB94CACABF4481F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_6BDFDB925C2484B31F774CACABF49191" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ABF21065C1EA6EC9DDB94CACABF4481F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ABF21065C1EA6EC9DDB94CACABF4481F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_6BDFDB925C2484B31F774CACABF49191" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ABF21065C1EA6EC9DDB94CACABF4481F" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_IntralinksHoldingsInc.Member" xlink:label="loc_sncr_IntralinksHoldingsInc.Member_3A0455191DAB8FF773EB4CACABF472D0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ABF21065C1EA6EC9DDB94CACABF4481F" xlink:to="loc_sncr_IntralinksHoldingsInc.Member_3A0455191DAB8FF773EB4CACABF472D0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_5DB550533F3B0B0B95FC4CACABF5DF89" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_DADB7B8BF678F90B2F614CACABEEFFDF" xlink:to="loc_us-gaap_AwardTypeAxis_5DB550533F3B0B0B95FC4CACABF5DF89" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_EF28F7CC3966E8C2C1214CACABF5B4D0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_5DB550533F3B0B0B95FC4CACABF5DF89" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_EF28F7CC3966E8C2C1214CACABF5B4D0_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_EF28F7CC3966E8C2C1214CACABF5B4D0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_5DB550533F3B0B0B95FC4CACABF5DF89" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_EF28F7CC3966E8C2C1214CACABF5B4D0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedStockMember" xlink:label="loc_us-gaap_RestrictedStockMember_3133BF4A90C175EE46764CACABF504A6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_EF28F7CC3966E8C2C1214CACABF5B4D0" xlink:to="loc_us-gaap_RestrictedStockMember_3133BF4A90C175EE46764CACABF504A6" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_EmployeeAndDirectorsStockOptionsMember" xlink:label="loc_sncr_EmployeeAndDirectorsStockOptionsMember_2250525B619DE4182F504CACABF63BC0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_EF28F7CC3966E8C2C1214CACABF5B4D0" xlink:to="loc_sncr_EmployeeAndDirectorsStockOptionsMember_2250525B619DE4182F504CACABF63BC0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PerformanceSharesMember" xlink:label="loc_us-gaap_PerformanceSharesMember_3363320D9C95D7B76AB04CACABF6C6EB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_EF28F7CC3966E8C2C1214CACABF5B4D0" xlink:to="loc_us-gaap_PerformanceSharesMember_3363320D9C95D7B76AB04CACABF6C6EB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_VestingAxis" xlink:label="loc_us-gaap_VestingAxis_D489E354EC8BC1E0B0864CACABF61137" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_DADB7B8BF678F90B2F614CACABEEFFDF" xlink:to="loc_us-gaap_VestingAxis_D489E354EC8BC1E0B0864CACABF61137" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_VestingDomain" xlink:label="loc_us-gaap_VestingDomain_295D016CD9BB171ACC774CACABF6B17B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_D489E354EC8BC1E0B0864CACABF61137" xlink:to="loc_us-gaap_VestingDomain_295D016CD9BB171ACC774CACABF6B17B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_VestingDomain" xlink:label="loc_us-gaap_VestingDomain_295D016CD9BB171ACC774CACABF6B17B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_D489E354EC8BC1E0B0864CACABF61137" xlink:to="loc_us-gaap_VestingDomain_295D016CD9BB171ACC774CACABF6B17B" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_QuarterlyVestingAfterFirstAnniversaryMember" xlink:label="loc_sncr_QuarterlyVestingAfterFirstAnniversaryMember_5F2BBDE5D4E2724AF4364CACABF6A819" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_295D016CD9BB171ACC774CACABF6B17B" xlink:to="loc_sncr_QuarterlyVestingAfterFirstAnniversaryMember_5F2BBDE5D4E2724AF4364CACABF6A819" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_VestingFirstAnniversaryMember" xlink:label="loc_sncr_VestingFirstAnniversaryMember_CBF78B1B76234F6CE0AF4CACABF6177B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_295D016CD9BB171ACC774CACABF6B17B" xlink:to="loc_sncr_VestingFirstAnniversaryMember_CBF78B1B76234F6CE0AF4CACABF6177B" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_VestingMonthlyContinuousServiceMember" xlink:label="loc_sncr_VestingMonthlyContinuousServiceMember_794A2BEAC2747F3D7CEC4CACABF72844" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_295D016CD9BB171ACC774CACABF6B17B" xlink:to="loc_sncr_VestingMonthlyContinuousServiceMember_794A2BEAC2747F3D7CEC4CACABF72844" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_VestingMonthlyContinuousServiceAfterSecondAnniversaryMember" xlink:label="loc_sncr_VestingMonthlyContinuousServiceAfterSecondAnniversaryMember_67DD4FC203339062CDF54CACABF7B54D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_295D016CD9BB171ACC774CACABF6B17B" xlink:to="loc_sncr_VestingMonthlyContinuousServiceAfterSecondAnniversaryMember_67DD4FC203339062CDF54CACABF7B54D" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_VestingPerformanceGoalAttainedMember" xlink:label="loc_sncr_VestingPerformanceGoalAttainedMember_3C9B6C1B885A6846F1CB4CACABF71556" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_295D016CD9BB171ACC774CACABF6B17B" xlink:to="loc_sncr_VestingPerformanceGoalAttainedMember_3C9B6C1B885A6846F1CB4CACABF71556" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_AnnualVestingOfPerformanceAwardsAfterInitialAchievementMember" xlink:label="loc_sncr_AnnualVestingOfPerformanceAwardsAfterInitialAchievementMember_ACE8A3B13D511A0C7F064CACABF7EFA8" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_295D016CD9BB171ACC774CACABF6B17B" xlink:to="loc_sncr_AnnualVestingOfPerformanceAwardsAfterInitialAchievementMember_ACE8A3B13D511A0C7F064CACABF7EFA8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="loc_us-gaap_PlanNameAxis_DF01F13C6526476548CE4CACABF7F9D5" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_DADB7B8BF678F90B2F614CACABEEFFDF" xlink:to="loc_us-gaap_PlanNameAxis_DF01F13C6526476548CE4CACABF7F9D5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_7594448712D5FBFDDF364CACABF84C15_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_DF01F13C6526476548CE4CACABF7F9D5" xlink:to="loc_us-gaap_PlanNameDomain_7594448712D5FBFDDF364CACABF84C15_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_7594448712D5FBFDDF364CACABF84C15" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_DF01F13C6526476548CE4CACABF7F9D5" xlink:to="loc_us-gaap_PlanNameDomain_7594448712D5FBFDDF364CACABF84C15" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_StockIncentive2000PlanMember" xlink:label="loc_sncr_StockIncentive2000PlanMember_C64628D22F219B3DA93D4CACABF8C751" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_7594448712D5FBFDDF364CACABF84C15" xlink:to="loc_sncr_StockIncentive2000PlanMember_C64628D22F219B3DA93D4CACABF8C751" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_EquityIncentivePlan2015Member" xlink:label="loc_sncr_EquityIncentivePlan2015Member_D1098DC9440A334243634CACABF8A8D2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_7594448712D5FBFDDF364CACABF84C15" xlink:to="loc_sncr_EquityIncentivePlan2015Member_D1098DC9440A334243634CACABF8A8D2" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_StockIncentive2006PlanMember" xlink:label="loc_sncr_StockIncentive2006PlanMember_FE7563BE3499B42ED4A44CACABF9B208" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_7594448712D5FBFDDF364CACABF84C15" xlink:to="loc_sncr_StockIncentive2006PlanMember_FE7563BE3499B42ED4A44CACABF9B208" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_StockIncentive2010PlanMember" xlink:label="loc_sncr_StockIncentive2010PlanMember_6AFD2B9D8C058429D59D4CACABF9EED9" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_7594448712D5FBFDDF364CACABF84C15" xlink:to="loc_sncr_StockIncentive2010PlanMember_6AFD2B9D8C058429D59D4CACABF9EED9" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_StockIncentive2000And2006PlanMember" xlink:label="loc_sncr_StockIncentive2000And2006PlanMember_B3F36C1253885BAEB8434CACABF9213D" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_7594448712D5FBFDDF364CACABF84C15" xlink:to="loc_sncr_StockIncentive2000And2006PlanMember_B3F36C1253885BAEB8434CACABF9213D" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_NewHireEquityIncentivePlan2017Member" xlink:label="loc_sncr_NewHireEquityIncentivePlan2017Member_ECFD9C7043A0D420F0954CB44695C5BC" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_7594448712D5FBFDDF364CACABF84C15" xlink:to="loc_sncr_NewHireEquityIncentivePlan2017Member_ECFD9C7043A0D420F0954CB44695C5BC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_7E7A51F576D4792015724CACABF93FBD" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_DADB7B8BF678F90B2F614CACABEEFFDF" xlink:to="loc_us-gaap_StatementClassOfStockAxis_7E7A51F576D4792015724CACABF93FBD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_3D26B2A356BD8B80AD334CACABF97801_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_7E7A51F576D4792015724CACABF93FBD" xlink:to="loc_us-gaap_ClassOfStockDomain_3D26B2A356BD8B80AD334CACABF97801_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_3D26B2A356BD8B80AD334CACABF97801" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_7E7A51F576D4792015724CACABF93FBD" xlink:to="loc_us-gaap_ClassOfStockDomain_3D26B2A356BD8B80AD334CACABF97801" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_09D764007B75446F97324CACABFAA35D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_3D26B2A356BD8B80AD334CACABF97801" xlink:to="loc_us-gaap_CommonStockMember_09D764007B75446F97324CACABFAA35D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SeriesAPreferredStockMember" xlink:label="loc_us-gaap_SeriesAPreferredStockMember_9A4BF11ECA12A6A608A04CACABFA6804" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_3D26B2A356BD8B80AD334CACABF97801" xlink:to="loc_us-gaap_SeriesAPreferredStockMember_9A4BF11ECA12A6A608A04CACABFA6804" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_5106F6443873EC84C7E04CACABFBFAE9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_5106F6443873EC84C7E04CACABFBFAE9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_4CEF7E0F236A372BB8844CACABFB2457" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_4CEF7E0F236A372BB8844CACABFB2457" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_NumberOfVotesPerShare" xlink:label="loc_sncr_NumberOfVotesPerShare_7185F4CC5973283401354CACABFB16AF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_NumberOfVotesPerShare_7185F4CC5973283401354CACABFB16AF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_Dividends" xlink:label="loc_us-gaap_Dividends_4DD128A83DAADDEDE1724CACABFB80F6" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_us-gaap_Dividends_4DD128A83DAADDEDE1724CACABFB80F6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_B6BF2F7484860DB320954CACABFC4418" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_B6BF2F7484860DB320954CACABFC4418" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_B83D14DDF1F7D6A91E7B4CACABFCF15D" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_B83D14DDF1F7D6A91E7B4CACABFCF15D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_D4ECC5BCE7461F23AA4B4CACABFC2E56" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_D4ECC5BCE7461F23AA4B4CACABFC2E56" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_6CAB6B7B4D3B67A311AF4CACABFC7840" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_6CAB6B7B4D3B67A311AF4CACABFC7840" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_BusinessCombinationPaymentofReimbursementFees" xlink:label="loc_sncr_BusinessCombinationPaymentofReimbursementFees_03DBBBA90A0C6B1342894CACABFCDEED" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_BusinessCombinationPaymentofReimbursementFees_03DBBBA90A0C6B1342894CACABFCDEED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PreferredStockDividendRatePercentage" xlink:label="loc_us-gaap_PreferredStockDividendRatePercentage_6EBDFBA651A4CCFF5CEB4CACABFD0C83" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_us-gaap_PreferredStockDividendRatePercentage_6EBDFBA651A4CCFF5CEB4CACABFD0C83" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_ConvertiblePreferredStockConversionPricePerShare" xlink:label="loc_sncr_ConvertiblePreferredStockConversionPricePerShare_2CBA6172299DBE5BE7A14CACABFD93FD" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_ConvertiblePreferredStockConversionPricePerShare_2CBA6172299DBE5BE7A14CACABFD93FD" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_NumberofElectedDirectors" xlink:label="loc_sncr_NumberofElectedDirectors_0601AE901DD04457CB794CACABFD3593" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_NumberofElectedDirectors_0601AE901DD04457CB794CACABFD3593" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_NumberOfBoardOfDirectorsElectedMeetingIndependenceCriteria" xlink:label="loc_sncr_NumberOfBoardOfDirectorsElectedMeetingIndependenceCriteria_9F420154EA6142B1397E4CACABFD9230" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_NumberOfBoardOfDirectorsElectedMeetingIndependenceCriteria_9F420154EA6142B1397E4CACABFD9230" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_PreferredStockOwnershipPercentage" xlink:label="loc_sncr_PreferredStockOwnershipPercentage_6FF63D1F4E68BA8598544CACABFDDEC5" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_PreferredStockOwnershipPercentage_6FF63D1F4E68BA8598544CACABFDDEC5" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_LongtermDebtFairValueApprovalThreshold" xlink:label="loc_sncr_LongtermDebtFairValueApprovalThreshold_03E2DCE5FD8B0F73BF574CACABFEF786" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_LongtermDebtFairValueApprovalThreshold_03E2DCE5FD8B0F73BF574CACABFEF786" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_FairMarketValueofTransactionIndividual" xlink:label="loc_sncr_FairMarketValueofTransactionIndividual_E6434C25A4B5A330E58A4CACABFEAC28" xlink:type="locator" />
    <link:definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_FairMarketValueofTransactionIndividual_E6434C25A4B5A330E58A4CACABFEAC28" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_FairMarketValueofTransactionAggregate" xlink:label="loc_sncr_FairMarketValueofTransactionAggregate_4AA81F4796FB9EA545EF4CACABFE31E8" xlink:type="locator" />
    <link:definitionArc order="17" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_FairMarketValueofTransactionAggregate_4AA81F4796FB9EA545EF4CACABFE31E8" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_CapitalExpenditureThreshold" xlink:label="loc_sncr_CapitalExpenditureThreshold_4E1C8C5AA2794AF059414CACABFE0FF0" xlink:type="locator" />
    <link:definitionArc order="18" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_CapitalExpenditureThreshold_4E1C8C5AA2794AF059414CACABFE0FF0" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_ConversionofStockPercentageOwnershipafterConversion" xlink:label="loc_sncr_ConversionofStockPercentageOwnershipafterConversion_513C60016CFD0ECFB25D4CACABFFB178" xlink:type="locator" />
    <link:definitionArc order="19" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_ConversionofStockPercentageOwnershipafterConversion_513C60016CFD0ECFB25D4CACABFFB178" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_ConversionofStockVotingPercentageThresholdofOwnership" xlink:label="loc_sncr_ConversionofStockVotingPercentageThresholdofOwnership_513FCFA78C97D0B3FCE34CACABFF74B9" xlink:type="locator" />
    <link:definitionArc order="20" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_ConversionofStockVotingPercentageThresholdofOwnership_513FCFA78C97D0B3FCE34CACABFF74B9" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_NumberOfBoardOfDirectorMembers" xlink:label="loc_sncr_NumberOfBoardOfDirectorMembers_0B2F0B2FA9C32FEAE47F4CACABFF0007" xlink:type="locator" />
    <link:definitionArc order="21" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_NumberOfBoardOfDirectorMembers_0B2F0B2FA9C32FEAE47F4CACABFF0007" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_NumberOfBoardOfDirectorMembersElectedByPreferredStockHolders" xlink:label="loc_sncr_NumberOfBoardOfDirectorMembersElectedByPreferredStockHolders_6AB823749E98A26428244CACABFFFD9F" xlink:type="locator" />
    <link:definitionArc order="22" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_NumberOfBoardOfDirectorMembersElectedByPreferredStockHolders_6AB823749E98A26428244CACABFFFD9F" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_NumberOfBoardOfDirectorsAgreedUponToBeElectedMeetingIndependenceCriteria" xlink:label="loc_sncr_NumberOfBoardOfDirectorsAgreedUponToBeElectedMeetingIndependenceCriteria_022DF5153C3401C2DCFE4CACABFF41FE" xlink:type="locator" />
    <link:definitionArc order="23" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_NumberOfBoardOfDirectorsAgreedUponToBeElectedMeetingIndependenceCriteria_022DF5153C3401C2DCFE4CACABFF41FE" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_MinimumNumberOfBoardOfDirectorMembersThatPreferredStockHoldersCanAppointPursuantToCertification" xlink:label="loc_sncr_MinimumNumberOfBoardOfDirectorMembersThatPreferredStockHoldersCanAppointPursuantToCertification_F1192B98F42C3C3597A24CACABFF1825" xlink:type="locator" />
    <link:definitionArc order="24" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_MinimumNumberOfBoardOfDirectorMembersThatPreferredStockHoldersCanAppointPursuantToCertification_F1192B98F42C3C3597A24CACABFF1825" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_MaximumOwnershipThresholdAllowedForDirectorElectionRightsPercent" xlink:label="loc_sncr_MaximumOwnershipThresholdAllowedForDirectorElectionRightsPercent_730ECDDA4B813C15ADC94CACABFFCE2C" xlink:type="locator" />
    <link:definitionArc order="25" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_MaximumOwnershipThresholdAllowedForDirectorElectionRightsPercent_730ECDDA4B813C15ADC94CACABFFCE2C" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_EquityAgreementDemandRegistrationsAllowedUnderAgreement" xlink:label="loc_sncr_EquityAgreementDemandRegistrationsAllowedUnderAgreement_859BEA36601A6D9C3A654CACAC00D544" xlink:type="locator" />
    <link:definitionArc order="26" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_EquityAgreementDemandRegistrationsAllowedUnderAgreement_859BEA36601A6D9C3A654CACAC00D544" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_EquityAgreementDemandRegistrationsAllowedUnderAgreementAnnually" xlink:label="loc_sncr_EquityAgreementDemandRegistrationsAllowedUnderAgreementAnnually_52843D0DA1451A784BAC4CACAC006579" xlink:type="locator" />
    <link:definitionArc order="27" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_EquityAgreementDemandRegistrationsAllowedUnderAgreementAnnually_52843D0DA1451A784BAC4CACAC006579" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_EquityAgreementDemandRegistrationMinimumPercentageOfShares" xlink:label="loc_sncr_EquityAgreementDemandRegistrationMinimumPercentageOfShares_B52AD44926EBD53F1E6A4CACAC0054FB" xlink:type="locator" />
    <link:definitionArc order="28" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_FF90396B5DC70271F37C4CACABFAF3E8" xlink:to="loc_sncr_EquityAgreementDemandRegistrationMinimumPercentageOfShares_B52AD44926EBD53F1E6A4CACAC0054FB" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/StockholdersEquityRestrictedStockDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_F1BC9F8DEB66167BECD647B86DF34F76" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_05E445F8347F488CBF8847B86DF105CE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_F1BC9F8DEB66167BECD647B86DF34F76" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_05E445F8347F488CBF8847B86DF105CE" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_6E81B292FF446F7212A147B86DF2959B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_05E445F8347F488CBF8847B86DF105CE" xlink:to="loc_us-gaap_AwardTypeAxis_6E81B292FF446F7212A147B86DF2959B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_301CDA0EAFBA64CFE9E147B86DF27F5B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_6E81B292FF446F7212A147B86DF2959B" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_301CDA0EAFBA64CFE9E147B86DF27F5B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_301CDA0EAFBA64CFE9E147B86DF27F5B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_6E81B292FF446F7212A147B86DF2959B" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_301CDA0EAFBA64CFE9E147B86DF27F5B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedStockMember" xlink:label="loc_us-gaap_RestrictedStockMember_06DD16C853FCC0099E7C47B86DF23969" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_301CDA0EAFBA64CFE9E147B86DF27F5B" xlink:to="loc_us-gaap_RestrictedStockMember_06DD16C853FCC0099E7C47B86DF23969" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_02EE0AF385961A1A0F9D47B86DF38F33" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_F1BC9F8DEB66167BECD647B86DF34F76" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_02EE0AF385961A1A0F9D47B86DF38F33" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_DCA1EC3FE837F292A3EC47B86DF3BC58" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_02EE0AF385961A1A0F9D47B86DF38F33" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_DCA1EC3FE837F292A3EC47B86DF3BC58" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_5D84466B050ECB16594C47B86DF30D98" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_02EE0AF385961A1A0F9D47B86DF38F33" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_5D84466B050ECB16594C47B86DF30D98" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_0561495CFBE8EF2D13C847B86DF488EE" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_02EE0AF385961A1A0F9D47B86DF38F33" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_0561495CFBE8EF2D13C847B86DF488EE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_ED888E0AD0D4C39C642747B86DF45519" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_02EE0AF385961A1A0F9D47B86DF38F33" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_ED888E0AD0D4C39C642747B86DF45519" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_7A9F384DCE266581EBDE47B86DF4C4FA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_F1BC9F8DEB66167BECD647B86DF34F76" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_7A9F384DCE266581EBDE47B86DF4C4FA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_393C34DBE9FE4515932A47B86DF43F49" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_7A9F384DCE266581EBDE47B86DF4C4FA" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_393C34DBE9FE4515932A47B86DF43F49" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_2831D7B297296020595547B86DF5C33F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_7A9F384DCE266581EBDE47B86DF4C4FA" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_2831D7B297296020595547B86DF5C33F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_39A6D2D3AB615142AE2E47B86DF540D3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_7A9F384DCE266581EBDE47B86DF4C4FA" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_39A6D2D3AB615142AE2E47B86DF540D3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_BAA93941312D6D8C011647B86DF54166" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract_7A9F384DCE266581EBDE47B86DF4C4FA" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_BAA93941312D6D8C011647B86DF54166" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/StockholdersEquityStockBasedCompensationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_46B4A1DF771344FD7918478FCBB6CBB8" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_B7D4C00230F6157DC4B6478FCBB25E3D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_46B4A1DF771344FD7918478FCBB6CBB8" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_B7D4C00230F6157DC4B6478FCBB25E3D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_BA9A490B0C6EA4C98B1C478FCBB3C04E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_B7D4C00230F6157DC4B6478FCBB25E3D" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_BA9A490B0C6EA4C98B1C478FCBB3C04E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_C13C1BA1EA5741C60413478FCBB3FC2B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_BA9A490B0C6EA4C98B1C478FCBB3C04E" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_C13C1BA1EA5741C60413478FCBB3FC2B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_C13C1BA1EA5741C60413478FCBB3FC2B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_BA9A490B0C6EA4C98B1C478FCBB3C04E" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_C13C1BA1EA5741C60413478FCBB3FC2B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_CostOfSalesMember" xlink:label="loc_us-gaap_CostOfSalesMember_35BA46A512864198BD70478FCBB3E803" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_C13C1BA1EA5741C60413478FCBB3FC2B" xlink:to="loc_us-gaap_CostOfSalesMember_35BA46A512864198BD70478FCBB3E803" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_53C230536653AD4AC842478FCBB4AF73" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_C13C1BA1EA5741C60413478FCBB3FC2B" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_53C230536653AD4AC842478FCBB4AF73" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_C36FEF2A3FB85D4A1B06478FCBB4D227" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_C13C1BA1EA5741C60413478FCBB3FC2B" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_C36FEF2A3FB85D4A1B06478FCBB4D227" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_A88F00BDAAAF539F9B76478FCBB43BCA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_B7D4C00230F6157DC4B6478FCBB25E3D" xlink:to="loc_us-gaap_AwardTypeAxis_A88F00BDAAAF539F9B76478FCBB43BCA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5DC3FB90A3265BA10D3A478FCBB44A04_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_A88F00BDAAAF539F9B76478FCBB43BCA" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5DC3FB90A3265BA10D3A478FCBB44A04_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5DC3FB90A3265BA10D3A478FCBB44A04" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_A88F00BDAAAF539F9B76478FCBB43BCA" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5DC3FB90A3265BA10D3A478FCBB44A04" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_EmployeeAndDirectorsStockOptionsMember" xlink:label="loc_sncr_EmployeeAndDirectorsStockOptionsMember_FFAFF461E2444C445309478FCBB494DC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5DC3FB90A3265BA10D3A478FCBB44A04" xlink:to="loc_sncr_EmployeeAndDirectorsStockOptionsMember_FFAFF461E2444C445309478FCBB494DC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedStockMember" xlink:label="loc_us-gaap_RestrictedStockMember_977D66005707E63641F7478FCBB51F43" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_5DC3FB90A3265BA10D3A478FCBB44A04" xlink:to="loc_us-gaap_RestrictedStockMember_977D66005707E63641F7478FCBB51F43" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_8AB238DE838528D9C8BF478FCBB50056" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_B7D4C00230F6157DC4B6478FCBB25E3D" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_8AB238DE838528D9C8BF478FCBB50056" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_A53F0BBEA55A38D47FB3478FCBB5C41C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_8AB238DE838528D9C8BF478FCBB50056" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_A53F0BBEA55A38D47FB3478FCBB5C41C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_A53F0BBEA55A38D47FB3478FCBB5C41C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_8AB238DE838528D9C8BF478FCBB50056" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_A53F0BBEA55A38D47FB3478FCBB5C41C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeStockMember" xlink:label="loc_us-gaap_EmployeeStockMember_BC9B51D3D9AD8D64EA38478FCBB56844" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_A53F0BBEA55A38D47FB3478FCBB5C41C" xlink:to="loc_us-gaap_EmployeeStockMember_BC9B51D3D9AD8D64EA38478FCBB56844" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_543392FCDD840B2D6EF2478FCBB62D48" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_46B4A1DF771344FD7918478FCBB6CBB8" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_543392FCDD840B2D6EF2478FCBB62D48" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_63E78EADC8FD84940519478FCBB675D1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_543392FCDD840B2D6EF2478FCBB62D48" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_63E78EADC8FD84940519478FCBB675D1" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_AllocatedSharebasedCompensationExpenseIncludingDiscontinuedOperations" xlink:label="loc_sncr_AllocatedSharebasedCompensationExpenseIncludingDiscontinuedOperations_E7067A9FA78E5A34BB41478FCBB7191C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_543392FCDD840B2D6EF2478FCBB62D48" xlink:to="loc_sncr_AllocatedSharebasedCompensationExpenseIncludingDiscontinuedOperations_E7067A9FA78E5A34BB41478FCBB7191C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_32B9B74784D95CBF408E478FCBB7214C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_543392FCDD840B2D6EF2478FCBB62D48" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense_32B9B74784D95CBF408E478FCBB7214C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_20A278F28619F60C8478478FCBB7B456" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_543392FCDD840B2D6EF2478FCBB62D48" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_20A278F28619F60C8478478FCBB7B456" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_BCDA131EE011EFECB6D2478FCBB7364D" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_543392FCDD840B2D6EF2478FCBB62D48" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_BCDA131EE011EFECB6D2478FCBB7364D" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/StockholdersEquityStockOptionsDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/StockholdersEquityTables" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_32ED20E36D59D6473173DC35EA928049" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_C638B1D55EC51C6F1202DC35EA91BDC3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_32ED20E36D59D6473173DC35EA928049" xlink:to="loc_us-gaap_StatementTable_C638B1D55EC51C6F1202DC35EA91BDC3" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_B20F1C3B6D059DA8812DDC35EA91D56B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_C638B1D55EC51C6F1202DC35EA91BDC3" xlink:to="loc_us-gaap_AwardTypeAxis_B20F1C3B6D059DA8812DDC35EA91D56B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_B28ECDF8543F401D55EDDC35EA91E5CC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_B20F1C3B6D059DA8812DDC35EA91D56B" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_B28ECDF8543F401D55EDDC35EA91E5CC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_B28ECDF8543F401D55EDDC35EA91E5CC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_B20F1C3B6D059DA8812DDC35EA91D56B" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_B28ECDF8543F401D55EDDC35EA91E5CC" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_EmployeeAndDirectorsStockOptionsMember" xlink:label="loc_sncr_EmployeeAndDirectorsStockOptionsMember_90A5C6039F9F8E235025DC35EA92924B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_B28ECDF8543F401D55EDDC35EA91E5CC" xlink:to="loc_sncr_EmployeeAndDirectorsStockOptionsMember_90A5C6039F9F8E235025DC35EA92924B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_RestrictedStockMember" xlink:label="loc_us-gaap_RestrictedStockMember_F45491341C84FE8F2AE6DC35EA9231C0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_B28ECDF8543F401D55EDDC35EA91E5CC" xlink:to="loc_us-gaap_RestrictedStockMember_F45491341C84FE8F2AE6DC35EA9231C0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfCompensationCostForShareBasedPaymentArrangementsAllocationOfShareBasedCompensationCostsByPlanTableTextBlock" xlink:label="loc_us-gaap_ScheduleOfCompensationCostForShareBasedPaymentArrangementsAllocationOfShareBasedCompensationCostsByPlanTableTextBlock_C89C0C461E2923572E0CDC35EA92A470" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_32ED20E36D59D6473173DC35EA928049" xlink:to="loc_us-gaap_ScheduleOfCompensationCostForShareBasedPaymentArrangementsAllocationOfShareBasedCompensationCostsByPlanTableTextBlock_C89C0C461E2923572E0CDC35EA92A470" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock" xlink:label="loc_us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock_B0A9A5D5429D86AF0BDCDC35EA9308E9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_32ED20E36D59D6473173DC35EA928049" xlink:to="loc_us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock_B0A9A5D5429D86AF0BDCDC35EA9308E9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock_E10373398417D2EEFD79DC35EA932971" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_32ED20E36D59D6473173DC35EA928049" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock_E10373398417D2EEFD79DC35EA932971" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGrantDateIntrinsicValueTableTextBlock" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGrantDateIntrinsicValueTableTextBlock_034BBF414B88195D0923DC35EA93C62B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_32ED20E36D59D6473173DC35EA928049" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGrantDateIntrinsicValueTableTextBlock_034BBF414B88195D0923DC35EA93C62B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ScheduleOfNonvestedShareActivityTableTextBlock" xlink:label="loc_us-gaap_ScheduleOfNonvestedShareActivityTableTextBlock_01E9598E326CBC5EEC3ADC35EA9387C6" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_32ED20E36D59D6473173DC35EA928049" xlink:to="loc_us-gaap_ScheduleOfNonvestedShareActivityTableTextBlock_01E9598E326CBC5EEC3ADC35EA9387C6" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/StockholdersEquityTreasuryStockDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_EquityClassOfTreasuryStockLineItems" xlink:label="loc_us-gaap_EquityClassOfTreasuryStockLineItems_93326A08483ABFBBE2DC421B7B2874CD" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ClassOfTreasuryStockTable" xlink:label="loc_us-gaap_ClassOfTreasuryStockTable_EFC348D9B501C2986BFC421B7B277AD2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_93326A08483ABFBBE2DC421B7B2874CD" xlink:to="loc_us-gaap_ClassOfTreasuryStockTable_EFC348D9B501C2986BFC421B7B277AD2" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareRepurchaseProgramAxis" xlink:label="loc_us-gaap_ShareRepurchaseProgramAxis_1070C23BA7A162FD4FF3421B7B279DB0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_EFC348D9B501C2986BFC421B7B277AD2" xlink:to="loc_us-gaap_ShareRepurchaseProgramAxis_1070C23BA7A162FD4FF3421B7B279DB0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_30696FEBABFB359EC273421B7B270971_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_1070C23BA7A162FD4FF3421B7B279DB0" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_30696FEBABFB359EC273421B7B270971_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_30696FEBABFB359EC273421B7B270971" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_1070C23BA7A162FD4FF3421B7B279DB0" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_30696FEBABFB359EC273421B7B270971" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_ShareRepurchaseProgram2016Member" xlink:label="loc_sncr_ShareRepurchaseProgram2016Member_F59B25911B297D1323C7421B7B27654F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareRepurchaseProgramDomain_30696FEBABFB359EC273421B7B270971" xlink:to="loc_sncr_ShareRepurchaseProgram2016Member_F59B25911B297D1323C7421B7B27654F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TreasuryStockNumberOfSharesAndRestrictionDisclosuresAbstract" xlink:label="loc_us-gaap_TreasuryStockNumberOfSharesAndRestrictionDisclosuresAbstract_2FEDD5C7764A166F799D421B7B288B7B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_93326A08483ABFBBE2DC421B7B2874CD" xlink:to="loc_us-gaap_TreasuryStockNumberOfSharesAndRestrictionDisclosuresAbstract_2FEDD5C7764A166F799D421B7B288B7B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_TreasuryStockSharesAcquired" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_61A14E5D6640120E742A421B7B28D386" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TreasuryStockNumberOfSharesAndRestrictionDisclosuresAbstract_2FEDD5C7764A166F799D421B7B288B7B" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_61A14E5D6640120E742A421B7B28D386" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/SubsequentEventsReview" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.synchronoss.com/role/SubsequentEventsReviewDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventLineItems" xlink:label="loc_us-gaap_SubsequentEventLineItems_BCBC99D0FA1F5791C6044226F222F590" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTable" xlink:label="loc_us-gaap_SubsequentEventTable_DACC15931BA8A301F2184226F21B7BD2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_BCBC99D0FA1F5791C6044226F222F590" xlink:to="loc_us-gaap_SubsequentEventTable_DACC15931BA8A301F2184226F21B7BD2" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_485F5CA1C500A9751B634227F05232C8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_DACC15931BA8A301F2184226F21B7BD2" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_485F5CA1C500A9751B634227F05232C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3A7B9E7461B24D177CD84227F0538007_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_485F5CA1C500A9751B634227F05232C8" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3A7B9E7461B24D177CD84227F0538007_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3A7B9E7461B24D177CD84227F0538007" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_485F5CA1C500A9751B634227F05232C8" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3A7B9E7461B24D177CD84227F0538007" xlink:type="arc" />
    <link:loc xlink:href="sncr-20180331.xsd#sncr_HoneybeeSoftwareMember" xlink:label="loc_sncr_HoneybeeSoftwareMember_D4D821FBFDB3DCF2FE65422844AF5FCD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3A7B9E7461B24D177CD84227F0538007" xlink:to="loc_sncr_HoneybeeSoftwareMember_D4D821FBFDB3DCF2FE65422844AF5FCD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_D78791A5B46F60B7C2B44226F21CBB51" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_DACC15931BA8A301F2184226F21B7BD2" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_D78791A5B46F60B7C2B44226F21CBB51" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_7598B9CB4FF4FBB1A1F04226F221C59D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_D78791A5B46F60B7C2B44226F21CBB51" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_7598B9CB4FF4FBB1A1F04226F221C59D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_7598B9CB4FF4FBB1A1F04226F221C59D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_D78791A5B46F60B7C2B44226F21CBB51" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_7598B9CB4FF4FBB1A1F04226F221C59D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_79CA6612266531D429A94227D37864EF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_7598B9CB4FF4FBB1A1F04226F221C59D" xlink:to="loc_us-gaap_SubsequentEventMember_79CA6612266531D429A94227D37864EF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2017/elts/us-gaap-2017-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_1D058C00FDBAD69971F4422751955F92" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_BCBC99D0FA1F5791C6044226F222F590" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_1D058C00FDBAD69971F4422751955F92" xlink:type="arc" />
  </link:definitionLink>
</link:linkbase>
