antifeedant Syllabification: (an·ti·feed·ant)Pronunciation: /ˌantēˈfēdnt, ˌantī-/Definition of antifeedant noun a naturally occurring substance in certain plants that adversely affects insects or other animals that eat them. Origin: 1960s: from anti- + feed + -antantifeedant in other Oxford dictionaries Definition of antifeedant in the British & World English dictionary