/ Dictionary / Index P perfidious: Meaning and Definition of Find definitions for: per•fid•i•ous Pronunciation: (pur-fid'ē-us), [key] — adj. deliberately faithless; treacherous; deceitful: a perfidious lover. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: perfidious (Thesaurus) perfervid perfidy Related Content Daily Word Quiz: deleterious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language