faithless

Definitions

Not to be relied upon; untrustworthy or disloyal.

Lacking religious belief or conviction.

Not true to one's marriage vows or partner; unfaithful.

Examples

The king was betrayed by his faithless advisors during the heat of the battle.

She felt heartbroken after discovering that her long-term partner had been faithless.

Synonyms

disloyal treacherous unfaithful perfidious untrustworthy fickle false

Antonyms

loyal faithful steadfast devoted trustworthy reliable constant