perfidious

adjective

per·​fid·​i·​ous (ˌ)pər-ˈfi-dē-əs How to pronounce perfidious (audio)
: of, relating to, or characterized by perfidy
perfidiously adverb
perfidiousness noun

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.

Choose the Right Synonym for 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

Examples of perfidious in a Sentence

We were betrayed by a perfidious ally. a perfidious campaign worker revealed the senator's strategy to his leading rival for the nomination
Recent Examples on the Web
These examples are automatically compiled from online sources to illustrate current usage. Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
And in this new era of Sino-Western rivalry, the Olympics are also used by more nationalistic elements of the Chinese media as a way to portray China in a positive light against the perfidious Americans and Europeans. Alexander Smith, NBC News, 11 Aug. 2024 If Washington’s forays are conspicuous and its aims perfidious, its partners will not abet the next undertaking. Mira Rapp-Hooper, Foreign Affairs, 3 Oct. 2019 In what might sound to many Americans like a familiar tactic, Netanyahu cast his critics and not himself as a threat to the country’s security, and sought to position himself as a victim of perfidious judges and prosecutors. Tracy Wilkinson, Los Angeles Times, 27 Mar. 2023 But writer Rob Engalla’s perfidious hand movements were their undoing. Vulture, 10 Mar. 2023 See all Example Sentences for perfidious 

Word History

First Known Use

1572, in the meaning defined above

Time Traveler
The first known use of perfidious was in 1572

Podcast

Dictionary Entries Near perfidious

Cite this Entry

“Perfidious.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/perfidious. Accessed 12 Nov. 2024.

Kids Definition

perfidious

adjective
per·​fid·​i·​ous (ˌ)pər-ˈfid-ē-əs How to pronounce perfidious (audio)
: of, relating to, or characterized by perfidy : treacherous
perfidiously adverb
perfidiousness noun

More from Merriam-Webster on perfidious

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!