Fidelity to one's lord or master; the feudal obligation by which the tenant or vassal was bound to be faithful to his lord.
The oath by which this obligation was assumed.
Unfaithfulness in some other moral obligation.
Lack of religious belief.
Unfaithfulness in a marriage or an intimate relationship: practice or instance of having a sexual or romantic affair with someone other than one's spouse, without the consent of the spouse.