- (a.) Guilty of perfidy; violating good faith or vows; false to trust or confidence reposed; teacherous; faithless; as, a perfidious friend.
- (a.) Involving or characterized by, perfidy.
Webster's Revised Unabridged Dictionary
| APA | Webster's. (2011). perfidious. Retrieved September 21, 2026, from http://smartdefine.org/perfidious/definitions/2043714 |
| Chicago | Webster's. 2011. "perfidious" http://smartdefine.org/perfidious/definitions/2043714 (accessed September 21, 2026). |
| Harvard | Webster's 2011, perfidious, Smart Define, viewed 21 September, 2026, <http://smartdefine.org/perfidious/definitions/2043714>. |
| MLA | Webster's. "perfidious" 27 May 2011. Web. 21 September 2026. <http://smartdefine.org/perfidious/definitions/2043714> |