treacherous

形容词 treacherous:

1. dangerously unstable and unpredictable
   同义词：unreliable
2. tending to betray; especially having a treacherous character as attributed to the Carthaginians by the Romans
   同义词：punic, perfidious

1. He is treacherous to his friends.
   他对他的朋友不忠。
2. You treacherous cur!
   你这个背信弃义的家伙！
3. He thinks that she is his friend, but she is treacherous.
   他认为她是他的朋友，但她是个奸诈的人。
4. My memory is treacherous.
   我的记忆靠不住。