Entry 1 sense Webster, 1913 Boastful /bōs'-tfəl/ · Boast·ful · IPA /ˈbəʊstfʊl/ 01 a. Given to, or full of, boasting; inclined to boast; vaunting; vainglorious; self-praising. 1. Given to, or full of, boasting; inclined to boast; vaunting; vainglorious; self-praising.