boastful adj. + Add to list US //ˈboʊstfəɫ// UK //bˈəʊstfəl// boast·ful SynonymsEtymology Synonyms bigbraggartbraggingbraggycock a hoopcrowingself aggrandizingOriginMEbostful→ENboastful From Middle English bostful, equivalent to boast + -ful.