Faithless

Faith"less, a. 1. Not believing; not giving credit.

Be not faithless, but believing.
John xx. 27.

2. Not believing on God or religion; specifically, not believing in the Christian religion. Shak.

3. Not observant of promises or covenants.

4. Not true to allegiance, duty, or vows; perfidious; trecherous; disloyal; not of true fidelity; inconstant, as a husband or a wife.

A most unnatural and faithless service.
Shak.

5. Serving to disappoint or deceive; delusive; unsatisfying. "Yonder faithless phantom." Goldsmith.

-- Faith"less*ly, adv.Faith"less*ness, n.