infest v. + Add to list US //ˌɪnˈfɛst// UK //ɪnfˈɛst// in·fest Archaic SynonymsEtymology Synonyms invadeoverrunOriginLATīnfestō→OFRinfester→MEinfesten→ENinfest From Middle English infesten, from Old French infester (“to infest”), from Latin īnfestō (“assail, molest”, verb), from īnfestus (“hostile”).