IPA: //ˈbʌmpʃəsnəs//
KK: /ˈbʌmpʃəsnəs/
The quality of being overly confident or proud, often in a way that is annoying to others.
His bumptiousness made it difficult for him to make friends at the new school.
Bumptiousness → It is formed from "bumptious" (from the dialectal English 'bumptious', meaning self-assertive or pushy) and "-ness" (meaning the state or quality of). The word "bumptiousness" refers to the quality of being self-assertive or overly confident in a way that is annoying.
Think of someone who is overly confident and assertive — that's what 'bumptiousness' means, the state of being pushy or self-important.