/ Thesaurus / P Synonyms of perfidiously Find synonyms for: Adverb1. perfidiouslyusage: in a perfidious manner; "he was playing perfidiously one side against the other"WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: winsome Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language