in a way that involves hurting somebody who trusts you 奸诈地: 以一种伤害包括信任你的人的方式The king had been treacherously murdered by his brother. 国王被他的兄弟背信弃义地谋杀了。
in a dangerous way, especially when something seems safer than it is 有潜在危险的 treacherously icy conditions on the roads 道路上背信弃义的结冰状况