perfidious

[per-fid-ee-uhs] / pərˈfɪd i əs /

ADJECTIVE

treacherous

Synonyms

WEAK

betraying deceitful deceptive double-crossing double-dealing faithless false insidious misleading recreant shifty slick snake in the grass traitorous two-faced two-timing undependable unfaithful unloyal unreliable untrustworthy

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Samuel Pepys knew him; the British diarist thought him “a perfidious rogue.”

From The Wall Street Journal • Mar. 11, 2026

The head of one of them, who preferred to remain anonymous, described it as a "perfidious and effective" strategy.

From Barron's • Nov. 1, 2025

“If the initial findings are confirmed, it will be a perfidious attack on our electricity infrastructure,” Stübgen said.

From Seattle Times • Mar. 5, 2024

He also exerts a malignant perfidious influence over people who are vulnerable to such energy and temptations, but for whatever reason have not yet fully surrendered to them.

From Salon • Feb. 2, 2024

Among the perfidious, the name of traitor is capital in itself.

From "The Left Hand of Darkness" by Ursula K. Le Guin

Vocabulary lists containing perfidious

The Vocabulary.com Top 1000

Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!

100 Top "SAT" Words

Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!

The Tempest

Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!