IPA: /ˈvɔːntfəl/
KK: /vɔntfəl/
Tending to brag or boast about oneself or one's achievements in a way that is showy or excessive.
His vauntful nature made it hard for others to take him seriously.
Vauntful → It is formed from "vaunt" (from Old French *vanter*, meaning to boast) and "-ful" (meaning full of). The word "vauntful" means full of boasting or prideful in one's achievements.
Think of someone who is 'full of boasting' — 'vaunt' means to boast, and '-ful' means full of.