noun
big lie; whopper
Refers to an outrageous, exaggerated lie or tall tale. Often used in the phrase 大ぼらを吹く (to tell a big lie/whopper).
彼はまた大ぼらを吹いている。
He's telling another big lie.
その話はどうせ大ぼらだろう。
That story is probably a whopper anyway.
From 大 (big) + ぼら (conch shell, tall tale). ぼら originally referred to a conch shell used as a horn, and by extension came to mean 'boasting' or 'tall tale'.