unfaithful

adj

1.
not true to duty or obligation or promises
trothless unanswerly
Antonym:
faithful
Derived from:
unfaithfulness
2.
having sexual relations with someone other than your husband or wife, or your boyfriend or girlfriend
bedswerving forlear forlearness forlier see OE leġe wedlock breach woughhammend
Antonym:
faithful
Derived from:
unfaithfulness
3.
having the character of, or characteristic of, a traitor
faithless traitorous treasonable treasonous
Derived from:
unfaithfulness
4.
not trustworthy