Shut up

"Shut up" is a direct command with a meaning very similar to "be quiet" and "be silent", but which is commonly perceived as a more forceful command to stop making noise or otherwise communicating, such as talking. The phrase is probably a shortened form of "shut up your mouth" or "shut your mouth up". Its use is generally considered rude and impolite, and may also be considered objectionable enough by some to be deemed inappropriate for formal proceedings.