astound v. + Add to list US //əˈstaʊnd// UK //ɐstˈaʊnd// as·tound Archaic SynonymsEtymology Synonyms amazeastonishOriginMEastouned→ENastound From Middle English astouned, astoned, astuned, past participle of astounen, astonen, astunen (“to astonish”). More at astonish.