na-adjective
exaggerated; overblown; overdone
Describes speech, behavior, reactions, or style that is overly dramatic, grandiose, or theatrical. Often used critically.
彼の大仰な身振りにはみんなうんざりしている。
Everyone is fed up with his exaggerated gestures.
そんな大仰な言い方をしなくてもいいよ。
You don't have to put it in such an overblown way.
The kanji 大 (big) and 仰 (look up, respect) combine to suggest an overblown, exaggerated manner. The exact historical derivation is uncertain.