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Synonyms

unfaithful

American  
[uhn-feyth-fuhl] / ʌnˈfeɪθ fəl /

adjective

  1. 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
  2. not sexually loyal to a spouse or lover; adulterous.

    She was concerned her husband would be unfaithful when he travelled.

  3. not accurate or complete; inexact.

    The book was an unfaithful translation of the original.

    Synonyms:
    untrue, imprecise
  4. Obsolete. without religious faith; unbelieving.


unfaithful British  
/ ʌnˈfeɪθfʊl /

adjective

  1. not true to a promise, vow, etc

  2. not true to a wife, husband, lover, etc, esp in having sexual intercourse with someone else

  3. inaccurate; inexact; unreliable; untrustworthy

    unfaithful copy

  4. obsolete not having religious faith; infidel

  5. obsolete not upright; dishonest

"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

Other Word Forms

Etymology

Origin of unfaithful

First recorded in 1350–1400; Middle English unfeithful, unfaithful; un- 1 + faithful ( def. )

Explanation

When someone is unfaithful, they're disloyal or unreliable. If you don't honor the pledge you made "to help people at all times," you're being unfaithful to the Girl Scout code. While it's common to use the word unfaithful for people who break their marriage vows, it's a great way to describe someone who's broken any serious promise or neglected an obligation. An elected government official who doesn't keep their promises to voters is an unfaithful public servant. And if your brother refuses to participate in the family's annual Halloween custom of dressing as pirates, you can say he's being unfaithful to the tradition.

Keep Reading on Vocabulary.com

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.

He found a film niche in the 1960s and 1970s playing ordinary Frenchmen with complicated personal lives in films like Unfaithful Wife and Just Before Night Fall.

From BBC • Apr. 13, 2022

On Unfaithful, you sing "April is the cruellest month" - but you're releasing the album in April.

From BBC • Apr. 24, 2018

Unfaithful Music and Disappearing Ink begins strongly with an evocative account of his father’s life as a crooner in 1960s England.

From The Guardian • Sep. 27, 2016

If there is any center to the sprawling, 670-page Unfaithful Music & Disappearing Ink—which free-associates on themes from Costello’s life without any obvious throughline, perhaps on the model of Bob Dylan’s Chronicles—it is that inheritance.

From Slate • Nov. 6, 2015

"Unfaithful servant!" he protested, glaring hard at Jemmy.

From "The Whipping Boy" by Sid Fleischman