deliberately faithless; treacherous; deceitful: a perfidious lover.

Origin of perfidious

First recorded in 1590–1600, perfidious is from the Latin word perfidiōsus faithless, dishonest. See perfidy, -ous
Related formsper·fid·i·ous·ly, adverbper·fid·i·ous·ness, nounun·per·fid·i·ous, adjectiveun·per·fid·i·ous·ly, adverbun·per·fid·i·ous·ness, noun

Synonyms for perfidious

Antonyms for perfidious Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for perfidiously

Historical Examples of perfidiously

British Dictionary definitions for perfidiously



guilty, treacherous, or faithless; deceitful
Derived Formsperfidiously, adverbperfidiousness, noun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for perfidiously



1590s, from Latin perfidiosus "treacherous," from perfidia (see perfidy). Related: Perfidiously; perfidiousness.

Online Etymology Dictionary, © 2010 Douglas Harper