IPA: /ˈboʊstfəl/
KK: /ˈboʊstfəl/
Having a tendency to brag or talk about one's achievements in a proud way.
His boastful attitude made it hard for others to enjoy the celebration.
Boastful → It is formed from "boast" (from Old French *boaster*, meaning to brag or show off) and "-ful" (meaning full of). The word "boastful" means full of boasting or characterized by bragging.
Think of someone who is 'full of bragging' — that's what 'boastful' means.