na. | 1. keep one's mouth shut as that of a jar; be as close as an oyster; be as silent as the grave; be buttoned up; be tight-mouthed; button [zip] one's lip; button up one's mouth; keep a still tongue in one's head; keep dumb as an oyster; keep [play] mum; keep one's lips buttoned; keep one's mouth closed [shut]; keep one's mouth tight as a jar lid; keep one's mouth tightly shut; keep one's tongue between one's teeth; never said a single word; stay tight-lipped |