BOASTFUL Meaning of BOASTFUL in English boast ‧ ful /ˈbəʊstf ə l $ ˈboʊst-/ BrE AmE adjective talking too proudly about yourself OPP modest—boastfully adverb—boastfulness noun [uncountable] Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012