undercover

臥底的、喬裝的

An undercover officer spent two years inside the gang.

一名臥底警員在幫派裡待了兩年。

祕密的、暗中進行的

The police launched an undercover investigation into the bribes.

警方針對這些賄款展開祕密調查。

臥底、祕密地

She went undercover to expose the illegal dumping.

她喬裝臥底，揭露非法棄置廢棄物的行為。