Definitions

1. adjective

not faithful or loyal; disloyal or untrustworthy

“She accused him of being unfaithful to their marriage vows.”

2. adverb

in a way that is not faithful or loyal

“He behaved unfaithfully towards his friend who had helped him in need.”

3. noun

a person who is unfaithful to their partner or spouse

“The unfaithful husband’s infidelity was a shock to his family.”