Like a traitor; involving treachery; violating allegiance or faith pledged; traitorous to the state or sovereign; perfidious in private life; betraying a trust; faithless.
- Marked by betrayal of fidelity, confidence, or trust; perfidious. See Synonyms at faithless.
- Not to be relied on; not dependable or trustworthy.
- Marked by unforeseen hazards; dangerous or deceptive: treacherous waters.