(as) hard as a rock

(as) hard as a rock

Very hard. I can't use this pillow, it's hard as a rock!

See also: hard, rock

Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

*hard as a rock

 and *hard as stone

very hard. (*Also: as ∼.) This cake is as hard as a rock! I can't drive a nail into this wood. It's hard as stone.

See also: hard, rock

McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.