1. guilty of or involving betrayal or deception
2. having hidden or unpredictable dangers

Examples

• The spy’s treacherous actions endangered national security.
• She felt betrayed by her friend’s treacherous behavior.
• The mountain path became treacherous in the fog.
• Ice made the roads treacherous for drivers.
• The treacherous currents caught the swimmers off guard.
• His treacherous smile hid his true intentions.
• The treacherous terrain slowed their progress.