perfidious

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

Definition of perfidious

:of, relating to, or characterized by perfidy

perfidiously

adverb

perfidiousness

noun

perfidious was our Word of the Day on 07/11/2010. Hear the podcast!

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

Recent Examples of perfidious from the Web

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.

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.

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

PERFIDIOUS Defined for English Language Learners

perfidious

adjective

Definition of perfidious for English Language Learners

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



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