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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:01a0b171-d58f-78b5-9a90-c74d73c9ed1d,g:a483da1c-80bc-4d3f-8526-25ac31bcc8d1-->
<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_ck0001137360_S000109338Member_01a0b171-d58f-7ecc-8228-d83160af5092" xlink:href="ck0001137360-20260923.xsd#ck0001137360_S000109338Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain" xlink:to="loc_ck0001137360_S000109338Member_01a0b171-d58f-7ecc-8228-d83160af5092" xlink:type="arc" order="1"/>
  </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_ck0001137360_C000161562Member_01a0b171-d58f-777d-9a56-00e4ab33f56f" xlink:href="ck0001137360-20260923.xsd#ck0001137360_C000161562Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_ShareClassDomain" xlink:to="loc_ck0001137360_C000161562Member_01a0b171-d58f-777d-9a56-00e4ab33f56f" xlink:type="arc" order="1"/>
  </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_ck0001137360_DefinedOutcomeStrategyRiskMember_01a0b177-4d9c-7989-91f1-eba33b26a392" xlink:href="ck0001137360-20260923.xsd#ck0001137360_DefinedOutcomeStrategyRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_DefinedOutcomeStrategyRiskMember_01a0b177-4d9c-7989-91f1-eba33b26a392" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_DefinedOutcomeStrategyRiskBufferedLossRiskMember_01a0b17e-1427-7d5d-9552-a4a7d3314bb3" xlink:href="ck0001137360-20260923.xsd#ck0001137360_DefinedOutcomeStrategyRiskBufferedLossRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_DefinedOutcomeStrategyRiskBufferedLossRiskMember_01a0b17e-1427-7d5d-9552-a4a7d3314bb3" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_DefinedOutcomeStrategyRiskCappedUpsideReturnRiskMember_01a0b17e-4a2d-718b-b8c4-bdb39a03f0a2" xlink:href="ck0001137360-20260923.xsd#ck0001137360_DefinedOutcomeStrategyRiskCappedUpsideReturnRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_DefinedOutcomeStrategyRiskCappedUpsideReturnRiskMember_01a0b17e-4a2d-718b-b8c4-bdb39a03f0a2" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_DefinedOutcomeStrategyRiskOutcomePeriodRiskMember_01a0b17e-8349-72fa-86db-ae318aaf38f3" xlink:href="ck0001137360-20260923.xsd#ck0001137360_DefinedOutcomeStrategyRiskOutcomePeriodRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_DefinedOutcomeStrategyRiskOutcomePeriodRiskMember_01a0b17e-8349-72fa-86db-ae318aaf38f3" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_DefinedOutcomeStrategyRiskUpsideParticipationRiskMember_01a0b17e-b653-701d-86e0-5fe96e65d2e2" xlink:href="ck0001137360-20260923.xsd#ck0001137360_DefinedOutcomeStrategyRiskUpsideParticipationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_DefinedOutcomeStrategyRiskUpsideParticipationRiskMember_01a0b17e-b653-701d-86e0-5fe96e65d2e2" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_DefinedOutcomeStrategyRiskCapChangeRiskMember_01a0b17e-ebed-7de9-9d16-cf23bef7ddbf" xlink:href="ck0001137360-20260923.xsd#ck0001137360_DefinedOutcomeStrategyRiskCapChangeRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_DefinedOutcomeStrategyRiskCapChangeRiskMember_01a0b17e-ebed-7de9-9d16-cf23bef7ddbf" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_DefinedOutcomeStrategyRiskBufferChangeRiskMember_01a0b17f-1f54-766f-b542-2a1f855b11f2" xlink:href="ck0001137360-20260923.xsd#ck0001137360_DefinedOutcomeStrategyRiskBufferChangeRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_DefinedOutcomeStrategyRiskBufferChangeRiskMember_01a0b17f-1f54-766f-b542-2a1f855b11f2" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_FLEXOptionsRiskMember_01a0b180-e7f0-75f2-8137-2fe3e891774c" xlink:href="ck0001137360-20260923.xsd#ck0001137360_FLEXOptionsRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_FLEXOptionsRiskMember_01a0b180-e7f0-75f2-8137-2fe3e891774c" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_OptionContractsRiskMember_01a0b181-1dbb-7d83-9637-f0ee708c904d" xlink:href="ck0001137360-20260923.xsd#ck0001137360_OptionContractsRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_OptionContractsRiskMember_01a0b181-1dbb-7d83-9637-f0ee708c904d" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_DerivativesRiskMember_01a0b181-55b4-77bf-9551-bb8e2fef17cd" xlink:href="ck0001137360-20260923.xsd#ck0001137360_DerivativesRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_DerivativesRiskMember_01a0b181-55b4-77bf-9551-bb8e2fef17cd" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_ClearingMemberDefaultRiskMember_01a0b181-9768-7ae6-8aef-300e8ccc43ae" xlink:href="ck0001137360-20260923.xsd#ck0001137360_ClearingMemberDefaultRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_ClearingMemberDefaultRiskMember_01a0b181-9768-7ae6-8aef-300e8ccc43ae" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_CounterpartyRiskMember_01a0b181-d379-7f7c-9f46-63ecc0495bae" xlink:href="ck0001137360-20260923.xsd#ck0001137360_CounterpartyRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_CounterpartyRiskMember_01a0b181-d379-7f7c-9f46-63ecc0495bae" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_UnderlyingETFRiskMember_01a0b182-0f50-77f0-a0c4-4a3c80d53319" xlink:href="ck0001137360-20260923.xsd#ck0001137360_UnderlyingETFRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_UnderlyingETFRiskMember_01a0b182-0f50-77f0-a0c4-4a3c80d53319" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_UnderlyingETFRiskEquitySecuritiesRiskMember_01a0b182-45f7-7477-9468-c299b69f6c34" xlink:href="ck0001137360-20260923.xsd#ck0001137360_UnderlyingETFRiskEquitySecuritiesRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_UnderlyingETFRiskEquitySecuritiesRiskMember_01a0b182-45f7-7477-9468-c299b69f6c34" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_UnderlyingETFRiskInformationTechnologySectorRiskMember_01a0b182-7c55-7c1d-9103-86acdd4d2a1a" xlink:href="ck0001137360-20260923.xsd#ck0001137360_UnderlyingETFRiskInformationTechnologySectorRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_UnderlyingETFRiskInformationTechnologySectorRiskMember_01a0b182-7c55-7c1d-9103-86acdd4d2a1a" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_UnderlyingETFRiskLargeCapitalizationCompaniesRiskMember_01a0b182-b435-74ba-86e3-91535007c378" xlink:href="ck0001137360-20260923.xsd#ck0001137360_UnderlyingETFRiskLargeCapitalizationCompaniesRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_UnderlyingETFRiskLargeCapitalizationCompaniesRiskMember_01a0b182-b435-74ba-86e3-91535007c378" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_CorrelationRiskMember_01a0b183-c83f-717f-9e91-f32df77c0ba0" xlink:href="ck0001137360-20260923.xsd#ck0001137360_CorrelationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_CorrelationRiskMember_01a0b183-c83f-717f-9e91-f32df77c0ba0" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_ConcentrationRiskMember_01a0b184-0b2c-75b7-94d7-4939fb04571a" xlink:href="ck0001137360-20260923.xsd#ck0001137360_ConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_ConcentrationRiskMember_01a0b184-0b2c-75b7-94d7-4939fb04571a" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_InvestmentObjectiveRiskMember_01a0b184-4f1f-7a33-9adb-d5f24f664fe1" xlink:href="ck0001137360-20260923.xsd#ck0001137360_InvestmentObjectiveRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_InvestmentObjectiveRiskMember_01a0b184-4f1f-7a33-9adb-d5f24f664fe1" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_LiquidityRiskMember_01a0b184-89fc-70ef-84f5-2d472cde9b36" xlink:href="ck0001137360-20260923.xsd#ck0001137360_LiquidityRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_LiquidityRiskMember_01a0b184-89fc-70ef-84f5-2d472cde9b36" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_MarketRiskMember_01a0b179-a479-70bf-9a23-dc593d77a238" xlink:href="ck0001137360-20260923.xsd#ck0001137360_MarketRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_MarketRiskMember_01a0b179-a479-70bf-9a23-dc593d77a238" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_TaxRiskMember_01a0b184-c5cc-7879-96ae-db6f26db8b25" xlink:href="ck0001137360-20260923.xsd#ck0001137360_TaxRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_TaxRiskMember_01a0b184-c5cc-7879-96ae-db6f26db8b25" xlink:type="arc" order="30"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_InvestingInETFsRiskMember_01a0b185-0fc2-7129-960c-cab3c05df50d" xlink:href="ck0001137360-20260923.xsd#ck0001137360_InvestingInETFsRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_InvestingInETFsRiskMember_01a0b185-0fc2-7129-960c-cab3c05df50d" xlink:type="arc" order="31"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_ActiveManagementRiskMember_01a0b185-4a1d-718f-81f2-c99ddad7308b" xlink:href="ck0001137360-20260923.xsd#ck0001137360_ActiveManagementRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_ActiveManagementRiskMember_01a0b185-4a1d-718f-81f2-c99ddad7308b" xlink:type="arc" order="32"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_SubAdviserRiskMember_01a0b185-8089-7e74-9422-bc0450d98df9" xlink:href="ck0001137360-20260923.xsd#ck0001137360_SubAdviserRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_SubAdviserRiskMember_01a0b185-8089-7e74-9422-bc0450d98df9" xlink:type="arc" order="33"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_AffiliatedFundInvestmentRiskMember_01a0b185-b84f-703c-b0d8-446a2651b0ca" xlink:href="ck0001137360-20260923.xsd#ck0001137360_AffiliatedFundInvestmentRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_AffiliatedFundInvestmentRiskMember_01a0b185-b84f-703c-b0d8-446a2651b0ca" xlink:type="arc" order="34"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_OperationalRiskMember_01a0b185-e7b6-754f-857d-2149f4d9f55a" xlink:href="ck0001137360-20260923.xsd#ck0001137360_OperationalRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_OperationalRiskMember_01a0b185-e7b6-754f-857d-2149f4d9f55a" xlink:type="arc" order="35"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_AuthorizedParticipantConcentrationRiskMember_01a0b186-1c84-77dc-9905-f1f64c284e79" xlink:href="ck0001137360-20260923.xsd#ck0001137360_AuthorizedParticipantConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_AuthorizedParticipantConcentrationRiskMember_01a0b186-1c84-77dc-9905-f1f64c284e79" xlink:type="arc" order="36"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_NewFundRiskMember_01a0b186-50f9-77e7-bdac-62edd38498da" xlink:href="ck0001137360-20260923.xsd#ck0001137360_NewFundRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_NewFundRiskMember_01a0b186-50f9-77e7-bdac-62edd38498da" xlink:type="arc" order="37"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_CashTransactionsRiskMember_01a0b186-823c-73b9-85aa-4ef7c916817d" xlink:href="ck0001137360-20260923.xsd#ck0001137360_CashTransactionsRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_CashTransactionsRiskMember_01a0b186-823c-73b9-85aa-4ef7c916817d" xlink:type="arc" order="38"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_NoGuaranteeOfActiveTradingMarketRiskMember_01a0b186-b875-7f78-9d3d-5fa65191f836" xlink:href="ck0001137360-20260923.xsd#ck0001137360_NoGuaranteeOfActiveTradingMarketRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_NoGuaranteeOfActiveTradingMarketRiskMember_01a0b186-b875-7f78-9d3d-5fa65191f836" xlink:type="arc" order="39"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_TradingIssuesRiskMember_01a0b186-ee7a-75b1-a48d-4ea500a764f1" xlink:href="ck0001137360-20260923.xsd#ck0001137360_TradingIssuesRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_TradingIssuesRiskMember_01a0b186-ee7a-75b1-a48d-4ea500a764f1" xlink:type="arc" order="40"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_FundSharesTradingPremiumDiscountRiskAndLiquidityOfFundSharesRiskMember_01a0b187-5a26-7ada-93f7-ab98b1d81da6" xlink:href="ck0001137360-20260923.xsd#ck0001137360_FundSharesTradingPremiumDiscountRiskAndLiquidityOfFundSharesRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_FundSharesTradingPremiumDiscountRiskAndLiquidityOfFundSharesRiskMember_01a0b187-5a26-7ada-93f7-ab98b1d81da6" xlink:type="arc" order="41"/>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001137360_ValuationRiskMember_01a0b17a-f14a-777a-b386-cb9b4cadc833" xlink:href="ck0001137360-20260923.xsd#ck0001137360_ValuationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oef_AllRisksMember" xlink:to="loc_ck0001137360_ValuationRiskMember_01a0b17a-f14a-777a-b386-cb9b4cadc833" xlink:type="arc" order="42"/>
  </link:definitionLink>
</link:linkbase>
