mouth off

US /maʊθ ɔf/
UK /maʊθ ɔf/
"mouth off" picture
1.

口答えする, 生意気な口をきく

to speak in an insolent or disrespectful way, especially to someone in authority

:
He got fired for mouthing off to his boss.
彼は上司に口答えしたため解雇された。
Don't mouth off to your elders.
年長者に口答えするな