undercover

[ uhn-der-kuhv-er, uhn-der-kuhv- ]

/ ˌʌn dərˈkʌv ər, ˈʌn dərˌkʌv- /

working or done out of public sight; secret: an undercover investigation.

engaged in spying or securing confidential information: an undercover agent.

Origin of undercover

First recorded in 1850–55; under- + cover

1 concealed, covert, clandestine, hidden.

A 19-year-old woman was killed in September after an undercover police watched a drug deal go down in Oklahoma City.

The 14 Teens Killed by Cops Since Michael Brown |Nina Strochlic |November 25, 2014 |DAILY BEAST
“We have undercover security,” says Vincent Zurzolo, the suave man in the blue suit in booth 2630 of New York Comic Con.

The Holy Grail of Comic Books Hid in Plain Site at New York Comic Con |Sujay Kumar |October 14, 2014 |DAILY BEAST
If you were to have undercover security, Comic Con is the perfect site.

The Holy Grail of Comic Books Hid in Plain Site at New York Comic Con |Sujay Kumar |October 14, 2014 |DAILY BEAST
Others seemed to be performing bombastic recitals of their grievances as if they were ill-trained actors or undercover agents.

Hong Kong Between Calm and Chaos |Ben Leung |October 3, 2014 |DAILY BEAST

Undercover detective Gustav Frank sold Mandelbaum several bolts of stolen silk that had been secretly marked.

Meet 'The Queen of Thieves' Marm Mandelbaum, New York City's First Mob Boss |J. North Conway |September 7, 2014 |DAILY BEAST
Well, it's a combination of vice, narcotics, and undercover work.

Warren Commission (7 of 26): Hearings Vol. VII (of 15) |The President's Commission on the Assassination of President Kennedy
Of course there were undercover agents on Zarathustra, hundreds of them.

Little Fuzzy |Henry Beam Piper
The Federation's undercover boys have been scanning the Devagas worlds and Tranest very closely of late, naturally.

Legacy |James H Schmitz
He realized almost at once that such an unknown, undercover echelon would be a must.

Man of Many Minds |E. Everett Evans
Would you clarify for me, someone is of the opinion that I thought that Oswald was an undercover agent for whom?

Warren Commission (3 of 26): Hearings Vol. III (of 15) |The President's Commission on the Assassination of President Kennedy

undercover

/ (ˌʌndəˈkʌvə) /

done or acting in secret undercover operations