/ Thesaurus / S Synonyms of sound asleep Find synonyms for: Adjective1. fast asleep(predicate), sound asleep(predicate), asleep(predicate) (vs. awake)usage: sleeping deeply; "lying fast asleep on the sofa"; "it would be cruel to wake him; he's sound asleep"WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: neologism Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language