quiet as a mouse and *quiet as the grave

(as) quiet as a mouse

Silent, meek, and gentle. I just can't believe that Kate actually yelled at Mike—she's usually as quiet as a mouse! We remained as quiet as mice to avoid being detected by the guards.
See also: mouse, quiet

*quiet as a (church) mouse and *quiet as the grave

very quiet. (*Also: as ~.) You'd better be as quiet as a mouse while Grandma takes her nap so you won't wake her up. This town is quiet as the grave now that the factories have closed.
See also: and, grave, mouse, quiet