- failing to observe the terms of a vow, promise, understanding, etc., or false to allegiance or duty; faithless; disloyal
- not true, accurate, or reliable; untrustworthy
- engaging in sexual relations with someone other than one's spouse, lover, etc.; adulterous
- Archaic lacking good faith; dishonest
- Obs. infidel
- a. Not adhering to promises, obligations, or allegiances; disloyal. See Synonyms at faithless.b. Breaking trust in a marriage or relationship by having sexual relations with someone other than one's spouse or sexual partner.
- Not justly representing or reflecting the facts or a primary source; inaccurate: an account that was unfaithful to what really happened; a translation that was unfaithful to the original.
(comparative more unfaithful, superlative most unfaithful)
From un- +"Ž faithful