/ Thesaurus / M Synonyms of master key Find synonyms for: Noun1. passkey, passe-partout, master key, master, keyusage: key that secures entrance everywhereWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: penurious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language