Quantcast
Merriam-Webster Logo
  • Dictionary
  • Thesaurus
  • Scrabble
  • Spanish Central
  • Learner's Dictionary

perfidious

play
adjective per·fid·i·ous \(ˌ)pər-ˈfi-dē-əs\

Simple Definition of perfidious

  • : not able to be trusted : showing that someone cannot be trusted

Source: Merriam-Webster's Learner's Dictionary

Full Definition of perfidious

  1. :  of, relating to, or characterized by perfidy

perfidiously

adverb

perfidiousness

noun

Examples of perfidious in a sentence

  1. We were betrayed by a perfidious ally.

  2. <a perfidious campaign worker revealed the senator's strategy to his leading rival for the nomination>



Did You Know?

We wouldn't lie to you about the history of "perfidious" - even though the word itself suggests deceitfulness. The modern English meaning of "perfidious" remains faithful to that of its Latin ancestor, perfidus, which means "faithless." English speakers have used "perfidious" to mean "treacherous" since at least 1572. One of the earliest known uses of the term can be found in Act V, scene iii of Shakespeare’s All's Well That Ends Well: the "perfidious slave" Parolles is thought to be an unreliable witness; he’ll say whatever suits his purpose, whether true or not. In contemporary usage, "perfidious" not only implies treacherousness, but an inability to be reliable or honorable.

1572

First Known Use of perfidious

1572

Synonym Discussion of perfidious

faithless, false, disloyal, traitorous, treacherous, perfidious mean untrue to what should command one's fidelity or allegiance. faithless applies to any failure to keep a promise or pledge or any breach of allegiance or loyalty <faithless allies>. false stresses the fact of failing to be true in any manner ranging from fickleness to cold treachery <betrayed by false friends>. disloyal implies a lack of complete faithfulness to a friend, cause, leader, or country <disloyal to their country>. traitorous implies either actual treason or a serious betrayal of trust <traitorous acts punishable by death>. treacherous implies readiness to betray trust or confidence <a treacherous adviser>. perfidious adds to faithless the implication of an incapacity for fidelity or reliability <a perfidious double-crosser>.

Rhymes with perfidious



Seen and Heard

What made you want to look up perfidious? Please tell us where you read or heard it (including the quote, if possible).

WORD OF THE DAY

to criticize in a loud and angry way

Get Word of the Day daily email!

WORD GAMES

Take a 3-minute break and test your skills!

confounded-person

Which is a synonym of indolent?

frenetic philistine lazy melancholy
Name That Thing

Test your visual vocabulary with our 10-question challenge!

TAKE THE QUIZ
SCRABBLE® Sprint

Test Your Knowledge - and learn some interesting things along the way.

TAKE THE QUIZ