unfaithful

adjective

un·​faith·​ful ˌən-ˈfāth-fəl 

: not faithful:

a

: not adhering to vows, allegiance, or duty : disloyal

an unfaithful friend

b

: not faithful to marriage vows

suspected her husband of being unfaithful

c

: inaccurate, untrustworthy

an unfaithful copy of a document

unfaithfully

ˌən-ˈfāth-fə-lē 

adverb

unfaithfulness noun

Synonyms

• disloyal
• faithless
• false
• fickle
• inconstant
• perfidious
• recreant
• traitorous
• treacherous
• untrue

Examples of unfaithful in a Sentence

colonists who later proved to be unfaithful to the cause of independence

Recent Examples on the Web

Already, reviews are raving about Lawrence’s performance as a woman who experiences postpartum depression and develops psychosis, opposite Robert Pattinson as her unfaithful husband. —Anna Cafolla, Vogue, 18 May 2025

Donald was repeatedly unfaithful and belittled his wife’s artistic side. —Stephen Rodrick, Rolling Stone, 18 May 2025

The two welcomed son Ever in March 2024 amid rocky times in their relationship Season 1 of The Secret Lives of Mormon Wives left fans waiting to hear about whether or not Dakota had been unfaithful Taylor Frankie Paul has walked a tough road with Dakota Mortensen. —Angela Andaloro, People.com, 15 May 2025

Deflection and a subtle jab about Angela’s allegedly unfaithful husband. —Shelby Stewart, Essence, 21 Apr. 2025

Word History

First Known Use

15th century, in the meaning defined above

Rhymes for unfaithful

• faithful

Kids Definition

unfaithful

adjective

un·​faith·​ful ˌən-ˈfāth-fəl 

ˈən-

1

: not observing vows, allegiance, or duty : disloyal

an unfaithful friend

2

: not faithful to marriage vows

3

: inaccurate

an unfaithful translation

unfaithfully

-fə-lē 

adverb

unfaithfulness noun