Adjective
[[]][Guilty of or involving betrayal or deception.]
The treacherous spy leaked the secret documents to the enemy.
Adjective
[[]][Hazardous because of hidden or unpredictable dangers.]
The mountain pass is treacherous during the winter months due to sudden ice storms.
Adjective
[[]][Unreliable or deceptive in appearance despite seeming safe.]
The river looked calm, but the current was treacherous and pulled the swimmer under.