indoor Syllabification: (in·door)Pronunciation: /ˈinˌdôr/Translate indoor | into French | into German | into Italian | into Spanish Definition of indoor adjective [attributive] situated, conducted, or used within a building or under cover:indoor sports of or relating to sports played indoors:the national indoor championOrigin: early 18th century (superseding earlier within-door): from in (as a preposition) + door. Compare with indoorsindoor in other Oxford dictionaries Definition of indoor in the British & World English dictionary