unfaithful
Americanadjective
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not faithful; false to duty, obligation, or promises; disloyal.
Given how unfaithful the party has been to voters, it would be surprising if they won.
- Synonyms:
- recreant, treacherous, deceitful, untrustworthy
-
not sexually loyal to a spouse or lover; adulterous.
She was concerned her husband would be unfaithful when he travelled.
-
not accurate or complete; inexact.
The book was an unfaithful translation of the original.
-
Obsolete. without religious faith; unbelieving.
adjective
-
not true to a promise, vow, etc
-
not true to a wife, husband, lover, etc, esp in having sexual intercourse with someone else
-
inaccurate; inexact; unreliable; untrustworthy
unfaithful copy
-
obsolete not having religious faith; infidel
-
obsolete not upright; dishonest
Other Word Forms
- unfaithfully adverb
- unfaithfulness noun
Etymology
Origin of unfaithful
First recorded in 1350–1400; Middle English unfeithful, unfaithful; un- 1 + faithful ( def. )
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Once the Games began, they were humiliated again by another kind of cheating scandal involving an unfaithful biathlete.
From The Wall Street Journal • Feb. 17, 2026
"And three months ago, I made the biggest mistake of my life and I was unfaithful," he continued.
From Barron's • Feb. 11, 2026
During the trial, Holly has been portrayed by him to be a nasty, unfaithful girlfriend who had multiple boyfriends, this could not be further from the truth.
From BBC • Nov. 1, 2024
The term “homewrecker” makes my skin crawl — probably because my dad was serially unfaithful to my mom, which I knew about for two reasons.
From Los Angeles Times • Mar. 22, 2024
He knew that Mae was unfaithful to him.
From "A Tree Grows in Brooklyn" by Betty Smith
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
