If the ground or sea is treacherous, it is extremely dangerous, especially because of bad weather conditions.

Snow and ice have left many roads treacherous, and drivers are warned to use caution. 冰雪使许多道路危机四伏，汽车司机被告诫要小心驾驶。

A person who is treacherous deceives someone who trusts them, or has no loyalty.

Vargas plays the part of a treacherous aristocrat who betrays his king and country. 瓦加斯扮演一个背叛了国王和祖国的不忠贵族。

I feel a bit treacherous to my own sex if I ever make general criticisms of women. 如果我泛泛地批评妇女，我会感到有点儿背叛自己的性别。