Bible Dictionary
FAITHLESS
Faithless means unbelieving, disbelieving, or lacking fidelity. Scripture uses the term both for those who refuse faith and, in some contexts, for those who prove unfaithful.
Biblical Usage
Jesus rebuked a faithless and perverse generation and commanded Thomas not to be faithless but believing. The word may also describe an unfaithful servant and, possibly, the unbelieving.