shut your trap
An imperative to be quiet or cease talking immediately. Can be rude, aggressive, or jocular depending on the context. Shut your trap, Bobby—no one asked for the opinion of a dork like you! A: "So, where do you think we can sell these stolen goods?" B: "Shut your trap! Don't you have enough sense not to talk about that in public?" Dave: "Wow, that Cadillac has seen better days. How much did you pay for that little gem?" Bill: "Ah, shut your trap, Dave. I think it looks just fine."