- The definition of perfidious is someone or something that cannot be trusted or that is dishonest.
A person who lies all the time is an example of someone who would be described as perfidious.
perfidious definition by Webster's New World
characterized by perfidy; treacherous
Origin: Classical Latin perfidiosus
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
- perfidiously adverb
perfidious definition by American Heritage Dictionary
Of, relating to, or marked by perfidy; treacherous. See Synonyms at faithless.
- per·fidˈi·ous·ly adverb