society > morality > duty or obligation > recognition of duty > undutifulness > unfaithfulness > [adverb] (8)
Unfaithfully, dishonestly; guilefully, treacherously. Obsolete.
Deceitfully, treacherously.
adv. Improperly; unfaithfully.
In an unfaithful manner; with lack of good faith.
In a faithless manner; unfaithfully; insincerely; in bad faith.
Faithlessly, perfidiously. Chiefly in to play (a person) false: to cheat in play; figurative to betray.