undercover

American  

[uhn-der-kuhv-er, uhn-der-kuhv-] / ˌʌn dərˈkʌv ər, ˈʌn dərˌkʌv- /

adjective

1. working or done out of public sight; secret.

   an undercover investigation.

   Synonyms:

   hidden, clandestine, covert

2. engaged in spying or securing confidential information.

   an undercover agent.

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undercover British  

/ ˌʌndəˈkʌvə /

adjective

1. done or acting in secret

   undercover operations

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Etymology

Origin of undercover

First recorded in 1850–55; under- + cover

Explanation

Undercover means secret or disguised. A police department might send undercover officers dressed as clowns to investigate a corrupt circus. When this adjective was originally used in the mid-19th century, it meant "sheltered beneath something," but after a century or so, it was routinely used to mean "covert or clandestine." If you go undercover, you're doing some kind of secret work, usually inside an organization or group. If the other chess club members want you to be an undercover spy inside the French club, you'll have to brush up on your verb tenses.

Example Sentences

Two people have been arrested in connection with a BBC undercover investigation into immigration advisers helping some asylum seekers pretend to be gay to stay in the country.

From BBC • May 6, 2026

In the undercover filming, Lubajja himself mentions the campaign and describes it as the scammers' "biggest problem".

From BBC • May 3, 2026

My favorite tribute is the surprisingly moving episode of “The Boondocks” called “Riley Wuz Here,” which presents its version of him as an undercover revolutionary called the Art Teacher.

From Salon • May 2, 2026

The director was reportedly set on posting a photo of himself and agents on social media, even though some of the British agents who were photographed work undercover.

From Salon • Apr. 24, 2026

So much for working undercover, but maybe this was better anyway.

From "Shelter (Book One): A Mickey Bolitar Novel" by Harlan Coben

Related Words

• covert