perfidious

American  

[per-fid-ee-uhs] / pərˈfɪd i əs /

adjective

1. deliberately faithless; treacherous; deceitful.

   a perfidious lover.

   Synonyms:

   traitorous, unfaithful, disloyal, false

   Antonyms:

   faithful

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perfidious British  

/ pəˈfɪdɪəs /

adjective

1. guilty, treacherous, or faithless; deceitful

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Other Word Forms

• perfidiously adverb
• perfidiousness noun
• unperfidious adjective
• unperfidiously adverb
• unperfidiousness noun

Etymology

Origin of perfidious

First recorded in 1530–40; from Latin perfidiōsus “faithless, dishonest”; perfidy, -ous

Example Sentences

And not just for the big-ticket impulse buys, either — mostly for the tiny, perfidious ones.

From Salon

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

From Barron's

“Behold, campers, this vile and destructive creature! This killer of songbirds! This murderer of chipmunks! This perfidious predator!”

From Literature

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

From Seattle Times

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