still as death
(as) still as death
Completely motionless; having no movement whatsoever. The forest was completely silent and still as death, and it sent shivers right down my spine. I remained as still as death so the burglar wouldn't know I was in the room.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
*still as death
Cliché immobile; completely still. (The reference to death gives this expression ominous connotations. *Also: as ~.) George sat as still as death all afternoon. When the storm was over, everything was suddenly still as death.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.