per·​fid·​i·​ous | \ (ˌ)pər-ˈfi-dē-əs How to pronounce perfidious (audio) \

Definition of perfidious

: of, relating to, or characterized by perfidy

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Other Words from perfidious

perfidiously adverb
perfidiousness noun

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

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.

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 Facebook and Twitter periodically purge perfidious propaganda-bots. Fortune Staff, Fortune, "2020 Crystal Ball: Predictions for the Economy, Politics, Technology, and More," 2 Dec. 2019 Some readers will find his rhetoric perfidious and reactionary, with its dismissal of identity politics and the concomitant particulars of the African-American experience. Andrew Solomon, New York Times, "How Moving to France and Having Children Led a Black American to Rethink Race," 18 Oct. 2019 Even Macron, for all his warnings about perfidious Albion, must realize that Europe’s high-pressure Brexit strategy hasn’t worked any wonders. Washington Post, "Theresa May Drags Europe Into Brexit’s Quicksand," 24 Sep. 2019 Soviet and Russian histories mark June 22nd 1941, when the perfidious Nazi invasion began. The Economist, "Poland’s forgotten heroism and suffering," 5 Sep. 2019 According to Barnum’s version of events, he was ruined by a perfidious business partner, who tricked him into endorsing half a million dollars’ worth of promissory notes. Elizabeth Kolbert, The New Yorker, "What P. T. Barnum Understood About America," 29 July 2019 But Gabbard has virtually no traction as a presidential candidate, owing to her own flakiness, illiberal record, and coziness with Syria’s perfidious, genocidal dictator, Bashar al-Assad. Adam Weinstein, The New Republic, "Most Veterans Say America’s Wars Are a Waste. No One’s Listening to Them.," 12 July 2019 The Germans and their Vichy puppets portrayed Dunkirk, where British forces helped evacuate over 300,000 people, not as the miracle spun by Winston Churchill that allowed Allied forces to regroup, but as a betrayal by the perfidious Brits. Sonia Purnell, Twin Cities, "Sonia Purnell: What D-Day teaches us about the difficulty – and importance – of resistance," 6 June 2019 The new heroes are black and white women determined to clean up the mess created by Fowler and his perfidious white financial backer. Tony Adler, Chicago Reader, "There’s a great play to be written about bigotry in Evanston in the early 20th century," 11 May 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'perfidious.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of perfidious

1572, in the meaning defined above

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The first known use of perfidious was in 1572

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Last Updated

17 Dec 2019

Cite this Entry

“Perfidious.” The Dictionary, Merriam-Webster Inc., Accessed 25 January 2020.

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More Definitions for perfidious


How to pronounce perfidious (audio)

English Language Learners Definition of perfidious

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

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More from Merriam-Webster on perfidious

Thesaurus: All synonyms and antonyms for perfidious

Rhyming Dictionary: Words that rhyme with perfidious

Spanish Central: Translation of perfidious

Nglish: Translation of perfidious for Spanish Speakers

Comments on perfidious

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


dull or mediocre

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