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

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

They were readily offered to our undercover researchers who secretly filmed in shops across four neighbouring West Midlands towns.

From BBC • Apr. 23, 2026

What our undercover voters are served by the algorithm is not a complete picture of what real Welsh voters are seeing online.

From BBC • Apr. 19, 2026

That evening the undercover reporter travelled to Forest Gate, in east London, for an initial consultation with Tanisa.

From BBC • Apr. 15, 2026

One day that September, the undercover operative who was pretending to be an insurance salesman stopped at a filling station in Fairfax and struck up a conversation with a woman working there.

From "Killers of the Flower Moon" by David Grann

Related Words

• covert