boast·ful \-fəl\adjective Etymology: Middle English boostful, bostful, from boost, bost boast + -ful : given to or marked by boasting < silly young officers, who talked in bellicose and boastful terms — Times Literary Supplement > • boast·ful·ly\-fəlē, -li\adverb • boast·ful·ness\-lnə̇s\noun-es