silent as the dead
(as) silent as the dead
Totally silent, especially as produces an ominous or foreboding effect. I knew something was wrong when I walked into the meeting room and all the members of the board were silent as the dead. I hate staying in my grandma's house. It gets as silent as the dead at nighttime, and it really creeps me out.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
*silent as the deadand *silent as the grave
completely silent. (Has ominous connotations because of the reference to death. Usually used to promise someone that you will be silent and therefore not betray a secret. *Also: as ~.) I knew something was wrong as soon as I entered the classroom; everyone was silent as the dead. Jessica is as silent as the grave on the subject of her first marriage. If you tell me what Katy said about me, I promise to be as silent as the grave.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.