noun
braggart; big talker; blowhard
A person who habitually tells exaggerated stories or boasts; often used in a derogatory or humorous way. The 大 (big) intensifies the base word ほら吹き (braggart).
See also: ホラ吹き
彼は大ぼら吹きだから、話を半分に聞いたほうがいいよ。
He's a big talker, so you'd better take what he says with a grain of salt.
あの大ぼら吹きの話を真に受ける人はいない。
Nobody takes that blowhard's stories seriously.
ほら吹き is the base word meaning 'braggart' or 'someone who tells tall tales'. 大ぼら吹き adds 大 (big) for emphasis, implying an even more exaggerated or habitual braggart.
Compound of 大 (big) + ほら吹き (braggart). ほら吹き itself comes from 法螺 (conch shell, also meaning 'tall tale') + 吹き (blowing), literally 'conch blower', referring to someone who 'blows' exaggerated stories.