undercover

1. ADJ Undercover work involves secretly obtaining information for the government or the police. 秘密的

...an undercover operation designed to catch drug smugglers. …一次为抓捕毒品走私贩而策划的秘密行动。

...undercover FBI agents. …联邦调查局的密探。

2. ADV Undercover is also an adverb. 秘密地[ADV after v]

Swanson persuaded Hubley to work undercover to capture the killer. 斯旺森说服了赫布利秘密工作以捕获凶手。