unfaithful Meaning, Definition & Usage

  1. adjective not true to duty or obligation or promises
    • an unfaithful lover
  2. adjective having sexual relations with someone other than your husband or wife, or your boyfriend or girlfriend
    • her husband was unfaithful
  3. adjective satellite having the character of, or characteristic of, a traitor
    treasonous; treasonable; traitorous; faithless.
    • the faithless Benedict Arnold
    • a lying traitorous insurrectionist
  4. adjective satellite not trustworthy
    • an unfaithful reproduction

WordNet

Un*faith"ful adjective
Definitions
  1. Not faithful; not observant of promises, vows, allegiance, or duty; violating trust or confidence; treacherous; perfidious; as, an unfaithful subject; an unfaithful agent or servant.
    My feet, through wine, unfaithful to their weight. Pope.
    His honor rooted in dishonor stood, And faith unfaithful kept him falsely true. Tennyson.
  2. Not possessing faith; infidel. R. Milton. -- Un*faith"ful*ly, adv. -- Un*faith"ful*ness, n.

Webster 1913