DictionaryuntrueNot faithful
adjective

untrue

Not loyal to a person or commitment.

He is untrue to his wife and hides the affair.

Etymology

True originally included faithfulness and reliability. Untrue preserves that loyalty sense in describing betrayal of a person or commitment.

More examples

  • She refuses to be untrue to her oldest friends.
  • Accepting the bribe would make him untrue to his principles.
  • He feels untrue to his team when he supports their rivals.

Forms

untrue · untruer · untruest

Similar words

disloyal
Emphasizes betrayal of a person, group, or cause.
unfaithful
Often refers specifically to cheating on a romantic partner.