treacherously
- r in a disloyal and faithless manner
he behaved treacherously
- Because of its unrelenting steepness and treacherously sudden storms, K2, known as the "Killer Mountain," is a formidable challenge for even accomplished climbers.
- Dug in under Israeli fire, Nasser, as he later wrote, reflected: "Here we are in these foxholes, surrounded, in danger, thrust treacherously into a battle we were not ready for .
- Predicting the future of a country as enigmatic and erratic as North Korea is a treacherously speculative pursuit.