1. The gang suspected that one of their members was a stool pigeon.
帮派怀疑他们的一名成员是告密者。
2. The police used a stool pigeon to gather evidence against the syndicate.
警方利用一名线人来收集针对该犯罪集团的证据。

A: Do you think he is working for the police?
A：你认为他在为警察工作吗？

B: I'm not sure, but he acts like a stool pigeon.
B：我不确定，但他表现得像个告密者。

1) 告密者

2) 线人

3) 内鬼

1. 告密者；线人

e.g. They caught him because he acted as a stool pigeon.
他们抓住了他，因为他充当了告密者。

noun

1. A person who provides secret information to the police or other authorities.

Synonym: informer, snitch, rat