Noah Webster
Unfaithful
UNFA'ITHFUL, adjective
1. 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.
2. Not performing the proper duty.
My feet through wine unfaithful to their weight -
3. Impious; infidel.
4. Negligent of duty; as an unfaithful workman.