Definition of perfidious
: of, relating to, or characterized by perfidy
perfidious was our Word of the Day on 07/11/2010. Hear the podcast!
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
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
Synonym Discussion of perfidious
PERFIDIOUS Defined for English Language Learners
Definition of perfidious for English Language Learners
: not able to be trusted : showing that someone cannot be trusted
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).