from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Marked by betrayal of fidelity, confidence, or trust; perfidious. See Synonyms at faithless.
- adj. Not to be relied on; not dependable or trustworthy.
- adj. Marked by unforeseen hazards; dangerous or deceptive: treacherous waters.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Exhibiting treachery.
- adj. Deceitful; inclined to betray.
- adj. Unreliable; dangerous.
from the GNU version of the Collaborative International Dictionary of English
- adj. Like a traitor; involving treachery; violating allegiance or faith pledged; traitorous to the state or sovereign; perfidious in private life; betraying a trust; faithless.
from The Century Dictionary and Cyclopedia
- Using treachery; violating allegiance or faith pledged; traitorous to the state or sovereign; perfidious in private life; betraying a trust.
- Marked by deceitfulness or perfidy; characteristic of a traitor.
- Having a good, fair, or sound appearance, but worthless or bad in character or quality; deceptive; not to be depended on or trusted.
- Synonyms Faithless, etc. (see perfidious), recreant, treasonable.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. tending to betray; especially having a treacherous character as attributed to the Carthaginians by the Romans
- adj. dangerously unstable and unpredictable
From treacher (Wiktionary)