住嘴 is an informal verb-object compound (离合词) literally meaning 'stop one's mouth'. It is a rude imperative equivalent to 'shut up' and is considered vulgar, suitable only for confrontational or very casual settings among close friends. The compound can be split: common patterns include 住你的嘴 ('shut your mouth') and 你给我住嘴 ('shut up for me'). Avoid using it in polite or professional contexts.