Synonyms of the word

perfidious

• adj. Of, pertaining to, or representing perfidy; disloyal to what should command one's fidelity or allegiance.

treacherous

• adj. Exhibiting treachery.
• adj. Deceitful; inclined to betray.
• adj. Unreliable; dangerous.

unfaithful

• adj. Not having religious faith.
• adj. Not keeping good faith; disloyal; not faithful.
• adj. Not honest or upright.
• adj. (translation studies) which doesn't faithfully render the meaning of the source language; incorrect.
• adj. Adulterous.