s conducted with or marked by hidden aims or methods
a. 秘密从事的, 秘密的, 从事间谍活动的
[法] 暗中从事的, 秘密的
1. The police officer worked undercover to catch the drug dealers.
警察卧底工作以抓住毒贩。
2. She wrote an undercover article about corruption in the city.
她撰写了一篇关于城市腐败的卧底文章。
3. He went undercover to investigate the company’s illegal activities.
他卧底调查公司的非法活动。