come off it!used to tell someone that you do not believe what they are saying
[TahlilGaran] Dictionary of Contemporary English ▲
come off it v. phr.,
slang Stop pretending; bragging, or kidding; stop being silly.
■ Used as a command.
"So I said to the duchess..." Jimmy began. "Oh, come off it," the other boys sneered. Fritz said he had a car of his own. "Oh, come off it," said John. "You can't even drive." [TahlilGaran] English Idioms Dictionary ▲