10-4 or Code 404? See How Well You Know Police Lingo and Terms
What does it mean when an officer is working "undercover"?

Correct Incorrect Undercover work means officers hide who they really are to get close to criminals without being noticed. It’s a key way to collect evidence while keeping the investigation secret. One famous example is FBI agent Joseph D. Pistone, who went undercover in the Mafia and inspired the movie Donnie Brasco.