<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019fd820-3d0e-7db0-be4a-fbacff4018e9,g:f7747796-6808-457b-8e0c-21f851267cae-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://xbrl.sec.gov/oef/role/SeriesOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#SeriesOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/oef/role/SeriesOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_S000107090Member_019fd820-3d0e-795f-90ff-ec5c08dc3417" xlink:href="ck0001540305-20260810.xsd#ck0001540305_S000107090Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain" xlink:to="loc_ck0001540305_S000107090Member_019fd820-3d0e-795f-90ff-ec5c08dc3417" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_S000107091Member_019fd820-3d0e-7302-8080-e5c03b7839b0" xlink:href="ck0001540305-20260810.xsd#ck0001540305_S000107091Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain" xlink:to="loc_ck0001540305_S000107091Member_019fd820-3d0e-7302-8080-e5c03b7839b0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_S000107092Member_019fd820-3d0e-7edd-aaac-cd2af0e88dc9" xlink:href="ck0001540305-20260810.xsd#ck0001540305_S000107092Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain" xlink:to="loc_ck0001540305_S000107092Member_019fd820-3d0e-7edd-aaac-cd2af0e88dc9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_S000107093Member_019fd820-3d0e-72d6-b039-e6daedf0f59b" xlink:href="ck0001540305-20260810.xsd#ck0001540305_S000107093Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain" xlink:to="loc_ck0001540305_S000107093Member_019fd820-3d0e-72d6-b039-e6daedf0f59b" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/oef/role/ClassOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#ClassOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/oef/role/ClassOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_oef_ShareClassDomain" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#oef_ShareClassDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_C000277977Member_019fd820-3d0e-76e4-94c6-d920bb26e449" xlink:href="ck0001540305-20260810.xsd#ck0001540305_C000277977Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_ShareClassDomain" xlink:to="loc_ck0001540305_C000277977Member_019fd820-3d0e-76e4-94c6-d920bb26e449" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_C000277978Member_019fd820-3d0e-74dc-96dd-b681a8837a47" xlink:href="ck0001540305-20260810.xsd#ck0001540305_C000277978Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_ShareClassDomain" xlink:to="loc_ck0001540305_C000277978Member_019fd820-3d0e-74dc-96dd-b681a8837a47" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_C000277979Member_019fd820-3d0e-75cf-8743-5540de14081d" xlink:href="ck0001540305-20260810.xsd#ck0001540305_C000277979Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_ShareClassDomain" xlink:to="loc_ck0001540305_C000277979Member_019fd820-3d0e-75cf-8743-5540de14081d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_C000277980Member_019fd820-3d0e-7910-8c24-d8e05e3ab831" xlink:href="ck0001540305-20260810.xsd#ck0001540305_C000277980Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_ShareClassDomain" xlink:to="loc_ck0001540305_C000277980Member_019fd820-3d0e-7910-8c24-d8e05e3ab831" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/rr/role/RiskOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#RiskOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/rr/role/RiskOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_oef_AllRisksMember" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#oef_AllRisksMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_AIInferenceTechnologiesIndustryRiskMember_019fd820-3d0e-7612-84b0-bf86677e37ca" xlink:href="ck0001540305-20260810.xsd#ck0001540305_AIInferenceTechnologiesIndustryRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_AIInferenceTechnologiesIndustryRiskMember_019fd820-3d0e-7612-84b0-bf86677e37ca" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_CollateralSecuritiesRiskMember_019fd820-3d0e-7fe4-a19f-8ab21202f5b9" xlink:href="ck0001540305-20260810.xsd#ck0001540305_CollateralSecuritiesRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_CollateralSecuritiesRiskMember_019fd820-3d0e-7fe4-a19f-8ab21202f5b9" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_ConcentrationRiskMember_019fd820-3d0e-74f9-8fa2-f96a85ab42b0" xlink:href="ck0001540305-20260810.xsd#ck0001540305_ConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_ConcentrationRiskMember_019fd820-3d0e-74f9-8fa2-f96a85ab42b0" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_ConcentrationRiskSemiconductorsIndustryRiskMember_019fd820-3d0e-7c91-b41a-74a3a109c4b7" xlink:href="ck0001540305-20260810.xsd#ck0001540305_ConcentrationRiskSemiconductorsIndustryRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_ConcentrationRiskSemiconductorsIndustryRiskMember_019fd820-3d0e-7c91-b41a-74a3a109c4b7" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_CounterpartyRiskMember_019fd820-3d0e-751a-b976-6b65d1248298" xlink:href="ck0001540305-20260810.xsd#ck0001540305_CounterpartyRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_CounterpartyRiskMember_019fd820-3d0e-751a-b976-6b65d1248298" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_CurrencyExchangeRateRiskMember_019fd820-3d0e-7d2d-8e56-f6c0e324aff4" xlink:href="ck0001540305-20260810.xsd#ck0001540305_CurrencyExchangeRateRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_CurrencyExchangeRateRiskMember_019fd820-3d0e-7d2d-8e56-f6c0e324aff4" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_CybersecurityRiskMember_019fd820-3d0e-7acf-b2b6-43061db84308" xlink:href="ck0001540305-20260810.xsd#ck0001540305_CybersecurityRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_CybersecurityRiskMember_019fd820-3d0e-7acf-b2b6-43061db84308" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_DepositaryReceiptRiskMember_019fd820-3d0e-7a11-bdd6-4ac1ceccbebd" xlink:href="ck0001540305-20260810.xsd#ck0001540305_DepositaryReceiptRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_DepositaryReceiptRiskMember_019fd820-3d0e-7a11-bdd6-4ac1ceccbebd" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_DerivativesRiskMember_019fd820-3d0e-7495-be7c-d82a88d13e10" xlink:href="ck0001540305-20260810.xsd#ck0001540305_DerivativesRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_DerivativesRiskMember_019fd820-3d0e-7495-be7c-d82a88d13e10" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_DerivativesRiskSwapAgreementsRiskMember_019fd820-3d0e-7e7c-81ab-31fdabf81eaa" xlink:href="ck0001540305-20260810.xsd#ck0001540305_DerivativesRiskSwapAgreementsRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_DerivativesRiskSwapAgreementsRiskMember_019fd820-3d0e-7e7c-81ab-31fdabf81eaa" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_DerivativesRiskSwapsCapacityRiskMember_019fd820-3d0e-73eb-98d2-b83c61bd739e" xlink:href="ck0001540305-20260810.xsd#ck0001540305_DerivativesRiskSwapsCapacityRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_DerivativesRiskSwapsCapacityRiskMember_019fd820-3d0e-73eb-98d2-b83c61bd739e" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_EmergingMarketsRiskMember_019fd820-3d0e-71f1-82d2-5cc832973321" xlink:href="ck0001540305-20260810.xsd#ck0001540305_EmergingMarketsRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_EmergingMarketsRiskMember_019fd820-3d0e-71f1-82d2-5cc832973321" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_EmergingMarketsRiskCapitalControlsAndSanctionsRiskMember_019fd820-3d0e-7ed5-afef-72846e1a6d45" xlink:href="ck0001540305-20260810.xsd#ck0001540305_EmergingMarketsRiskCapitalControlsAndSanctionsRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_EmergingMarketsRiskCapitalControlsAndSanctionsRiskMember_019fd820-3d0e-7ed5-afef-72846e1a6d45" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_EmergingMarketsRiskGeopoliticalRiskMember_019fd820-3d0e-72f2-af9c-6c3acbb99ff1" xlink:href="ck0001540305-20260810.xsd#ck0001540305_EmergingMarketsRiskGeopoliticalRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_EmergingMarketsRiskGeopoliticalRiskMember_019fd820-3d0e-72f2-af9c-6c3acbb99ff1" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_EmergingTechnologiesInvestmentRiskMember_019fd820-3d0e-78a4-8b00-c6778ee99fea" xlink:href="ck0001540305-20260810.xsd#ck0001540305_EmergingTechnologiesInvestmentRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_EmergingTechnologiesInvestmentRiskMember_019fd820-3d0e-78a4-8b00-c6778ee99fea" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_EquityMarketRiskMember_019fd820-3d0e-70f3-a4b6-eb2ae73380c0" xlink:href="ck0001540305-20260810.xsd#ck0001540305_EquityMarketRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_EquityMarketRiskMember_019fd820-3d0e-70f3-a4b6-eb2ae73380c0" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_ETFRisksMember_019fd820-3d0e-7353-8a2c-604e8243b632" xlink:href="ck0001540305-20260810.xsd#ck0001540305_ETFRisksMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_ETFRisksMember_019fd820-3d0e-7353-8a2c-604e8243b632" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_ETFRisksAuthorizedParticipantsMarketMakersAndLiquidityProvidersConcentrationRiskMember_019fd820-3d0e-713e-a363-7a4d5e30e1ec" xlink:href="ck0001540305-20260810.xsd#ck0001540305_ETFRisksAuthorizedParticipantsMarketMakersAndLiquidityProvidersConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_ETFRisksAuthorizedParticipantsMarketMakersAndLiquidityProvidersConcentrationRiskMember_019fd820-3d0e-713e-a363-7a4d5e30e1ec" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_ETFRisksCashRedemptionRiskMember_019fd820-3d0e-76b0-9f85-490dd2a5c924" xlink:href="ck0001540305-20260810.xsd#ck0001540305_ETFRisksCashRedemptionRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_ETFRisksCashRedemptionRiskMember_019fd820-3d0e-76b0-9f85-490dd2a5c924" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_ETFRisksCostsOfBuyingOrSellingSharesRiskMember_019fd820-3d0e-7c1e-897f-8eb73db28d5c" xlink:href="ck0001540305-20260810.xsd#ck0001540305_ETFRisksCostsOfBuyingOrSellingSharesRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_ETFRisksCostsOfBuyingOrSellingSharesRiskMember_019fd820-3d0e-7c1e-897f-8eb73db28d5c" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_ETFRisksSharesMayTradeAtPricesOtherThanNAVRiskMember_019fd820-3d0e-7f1f-a0c7-84ca7f77ad3e" xlink:href="ck0001540305-20260810.xsd#ck0001540305_ETFRisksSharesMayTradeAtPricesOtherThanNAVRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_ETFRisksSharesMayTradeAtPricesOtherThanNAVRiskMember_019fd820-3d0e-7f1f-a0c7-84ca7f77ad3e" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_ETFRisksTradingRiskMember_019fd820-3d0e-7600-8873-dbd6d36dae93" xlink:href="ck0001540305-20260810.xsd#ck0001540305_ETFRisksTradingRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_ETFRisksTradingRiskMember_019fd820-3d0e-7600-8873-dbd6d36dae93" xlink:type="arc" order="30"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_ForeignSecuritiesRiskMember_019fd820-3d0e-7b90-a8b8-5da3bef9131d" xlink:href="ck0001540305-20260810.xsd#ck0001540305_ForeignSecuritiesRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_ForeignSecuritiesRiskMember_019fd820-3d0e-7b90-a8b8-5da3bef9131d" xlink:type="arc" order="31"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_GeographicInvestmentRiskMember_019fd820-3d0e-749b-a6be-d9cc81a23a1c" xlink:href="ck0001540305-20260810.xsd#ck0001540305_GeographicInvestmentRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_GeographicInvestmentRiskMember_019fd820-3d0e-749b-a6be-d9cc81a23a1c" xlink:type="arc" order="32"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_IndexMethodologyRiskMember_019fd820-3d0e-7241-81bf-9e873d9cc0e3" xlink:href="ck0001540305-20260810.xsd#ck0001540305_IndexMethodologyRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_IndexMethodologyRiskMember_019fd820-3d0e-7241-81bf-9e873d9cc0e3" xlink:type="arc" order="33"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_IndexProviderRiskMember_019fd820-3d0e-766f-a325-6601d64a639e" xlink:href="ck0001540305-20260810.xsd#ck0001540305_IndexProviderRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_IndexProviderRiskMember_019fd820-3d0e-766f-a325-6601d64a639e" xlink:type="arc" order="34"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_MarketCapitalizationRiskMember_019fd820-3d0e-7cc9-96ad-d49694ce7592" xlink:href="ck0001540305-20260810.xsd#ck0001540305_MarketCapitalizationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_MarketCapitalizationRiskMember_019fd820-3d0e-7cc9-96ad-d49694ce7592" xlink:type="arc" order="35"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_MarketCapitalizationRiskLargeCapitalizationInvestingRiskMember_019fd820-3d0e-7fb4-91bd-49f32de06766" xlink:href="ck0001540305-20260810.xsd#ck0001540305_MarketCapitalizationRiskLargeCapitalizationInvestingRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_MarketCapitalizationRiskLargeCapitalizationInvestingRiskMember_019fd820-3d0e-7fb4-91bd-49f32de06766" xlink:type="arc" order="36"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_MarketCapitalizationRiskMidCapitalizationInvestingRiskMember_019fd820-3d0e-791d-ad43-238be768fc95" xlink:href="ck0001540305-20260810.xsd#ck0001540305_MarketCapitalizationRiskMidCapitalizationInvestingRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_MarketCapitalizationRiskMidCapitalizationInvestingRiskMember_019fd820-3d0e-791d-ad43-238be768fc95" xlink:type="arc" order="37"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_MarketCapitalizationRiskSmallCapitalizationInvestingRiskMember_019fd820-3d0e-7eca-8faa-a3f0732a6d87" xlink:href="ck0001540305-20260810.xsd#ck0001540305_MarketCapitalizationRiskSmallCapitalizationInvestingRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_MarketCapitalizationRiskSmallCapitalizationInvestingRiskMember_019fd820-3d0e-7eca-8faa-a3f0732a6d87" xlink:type="arc" order="38"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_NewFundRiskMember_019fd820-3d0e-71de-bde1-ef35865a860c" xlink:href="ck0001540305-20260810.xsd#ck0001540305_NewFundRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_NewFundRiskMember_019fd820-3d0e-71de-bde1-ef35865a860c" xlink:type="arc" order="39"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_PassiveInvestmentRiskMember_019fd820-3d0e-7965-9fb2-9eabc1bbc3f5" xlink:href="ck0001540305-20260810.xsd#ck0001540305_PassiveInvestmentRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_PassiveInvestmentRiskMember_019fd820-3d0e-7965-9fb2-9eabc1bbc3f5" xlink:type="arc" order="40"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_SectorRiskMember_019fd820-3d0e-7937-82d5-6f53f6c5b05c" xlink:href="ck0001540305-20260810.xsd#ck0001540305_SectorRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_SectorRiskMember_019fd820-3d0e-7937-82d5-6f53f6c5b05c" xlink:type="arc" order="41"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_SectorRiskInformationTechnologySectorRiskMember_019fd820-3d0e-742b-a878-bf19bed83aa7" xlink:href="ck0001540305-20260810.xsd#ck0001540305_SectorRiskInformationTechnologySectorRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_SectorRiskInformationTechnologySectorRiskMember_019fd820-3d0e-742b-a878-bf19bed83aa7" xlink:type="arc" order="42"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_TaxRiskMember_019fd820-3d0e-7d19-a28a-d4c680956229" xlink:href="ck0001540305-20260810.xsd#ck0001540305_TaxRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_TaxRiskMember_019fd820-3d0e-7d19-a28a-d4c680956229" xlink:type="arc" order="43"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_TrackingErrorRiskMember_019fd820-3d0e-7f82-9985-f31039b68bff" xlink:href="ck0001540305-20260810.xsd#ck0001540305_TrackingErrorRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_TrackingErrorRiskMember_019fd820-3d0e-7f82-9985-f31039b68bff" xlink:type="arc" order="44"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_AISemiconductorSpecializedPackagingAndTestingIndustryRiskMember_019fd820-3d0e-74f8-9af7-9c242630134b" xlink:href="ck0001540305-20260810.xsd#ck0001540305_AISemiconductorSpecializedPackagingAndTestingIndustryRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_AISemiconductorSpecializedPackagingAndTestingIndustryRiskMember_019fd820-3d0e-74f8-9af7-9c242630134b" xlink:type="arc" order="45"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_ChinaASharesRiskMember_019fd820-3d0e-7bfd-809c-aeefa0659408" xlink:href="ck0001540305-20260810.xsd#ck0001540305_ChinaASharesRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_ChinaASharesRiskMember_019fd820-3d0e-7bfd-809c-aeefa0659408" xlink:type="arc" order="46"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_GeographicInvestmentRiskRisksRelatedToInvestingInJapanRiskMember_019fd820-3d0e-7514-85c2-4f836f37c926" xlink:href="ck0001540305-20260810.xsd#ck0001540305_GeographicInvestmentRiskRisksRelatedToInvestingInJapanRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_GeographicInvestmentRiskRisksRelatedToInvestingInJapanRiskMember_019fd820-3d0e-7514-85c2-4f836f37c926" xlink:type="arc" order="47"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_GeographicInvestmentRiskRisksOfInvestingInTaiwanRiskMember_019fd820-3d0e-76fd-a1b3-3135d9393132" xlink:href="ck0001540305-20260810.xsd#ck0001540305_GeographicInvestmentRiskRisksOfInvestingInTaiwanRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_GeographicInvestmentRiskRisksOfInvestingInTaiwanRiskMember_019fd820-3d0e-76fd-a1b3-3135d9393132" xlink:type="arc" order="48"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_ConcentrationRiskDataStorageHardwareIndustryGroupRiskMember_019fd820-3d0e-761a-8282-09b47b9366ba" xlink:href="ck0001540305-20260810.xsd#ck0001540305_ConcentrationRiskDataStorageHardwareIndustryGroupRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_ConcentrationRiskDataStorageHardwareIndustryGroupRiskMember_019fd820-3d0e-761a-8282-09b47b9366ba" xlink:type="arc" order="49"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_ConcentrationRiskOptoelectronicsElectronicsComponentsIndustryGroupsRiskMember_019fd820-3d0e-7245-b533-637b91f4e07f" xlink:href="ck0001540305-20260810.xsd#ck0001540305_ConcentrationRiskOptoelectronicsElectronicsComponentsIndustryGroupsRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_ConcentrationRiskOptoelectronicsElectronicsComponentsIndustryGroupsRiskMember_019fd820-3d0e-7245-b533-637b91f4e07f" xlink:type="arc" order="50"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_ConcentrationRiskAirLiquidAndGasControlEquipmentIndustryGroupRiskMember_019fd820-3d0e-7cb8-baed-1ba7b5371b4e" xlink:href="ck0001540305-20260810.xsd#ck0001540305_ConcentrationRiskAirLiquidAndGasControlEquipmentIndustryGroupRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_ConcentrationRiskAirLiquidAndGasControlEquipmentIndustryGroupRiskMember_019fd820-3d0e-7cb8-baed-1ba7b5371b4e" xlink:type="arc" order="51"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_ConcentrationRiskSpecialtyContractingServicesIndustryGroupRiskMember_019fd820-3d0e-7e6b-85fe-78e5c527ba9f" xlink:href="ck0001540305-20260810.xsd#ck0001540305_ConcentrationRiskSpecialtyContractingServicesIndustryGroupRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_ConcentrationRiskSpecialtyContractingServicesIndustryGroupRiskMember_019fd820-3d0e-7e6b-85fe-78e5c527ba9f" xlink:type="arc" order="52"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001540305_SectorRiskMaterialsSectorRiskMember_019fd820-3d0e-78c3-bd66-f70db3c8426e" xlink:href="ck0001540305-20260810.xsd#ck0001540305_SectorRiskMaterialsSectorRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001540305_SectorRiskMaterialsSectorRiskMember_019fd820-3d0e-78c3-bd66-f70db3c8426e" xlink:type="arc" order="53"/>
  </link:definitionLink>
</link:linkbase>
