[ uhn-feyth-fuhl ]
/ ʌnˈfeɪθ fəl /


not faithful; false to duty, obligation, or promises; faithless; disloyal.
not sexually faithful to a spouse or lover.
not accurate or complete; inexact: an unfaithful translation.
Obsolete. unbelieving; infidel.

Origin of unfaithful

First recorded in 1350–1400, unfaithful is from the Middle English word unfeithful. See un-1, faithful

Related forms

un·faith·ful·ly, adverbun·faith·ful·ness, noun
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for unfaithfulness

British Dictionary definitions for unfaithfulness


/ (ʌnˈfeɪθfʊl) /


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; untrustworthyunfaithful copy
obsolete not having religious faith; infidel
obsolete not upright; dishonest

Derived Forms

unfaithfully, adverbunfaithfulness, noun
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