Not observant of promises, vows, allegiance or duty; violating trust or confidence; treacherous; perfidious; as an unfaithful subject; an unfaithful husband or wife; an unfaithful servant; an unfaithful bailee or agent.

Not performing the proper duty. My feet through wine unfaithful to their weight - .

Impious; infidel.

Negligent of duty; as an unfaithful workman.