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

Steve Coogan is terrific in a rare dramatic role, as is Tom Burke as cop teetering on the edge as he falls dangerously deep into his undercover persona.

From MarketWatch • May 31, 2026

When Conradt didn’t show at the undercover house, NBC and police went to his home in an attempt to serve a search warrant.

From Los Angeles Times • May 27, 2026

This time, an undercover researcher posed as a UK-based family member of a migrant attempting to cross the Channel.

From BBC • May 18, 2026

In March, an undercover agent contacted one of the participants to ask about the iRobot deal and other trades, pretending to be a securities regulator.

From The Wall Street Journal • May 12, 2026

Wasn’t that the name of the undercover agent who had stopped him in the rest room?

From "A Confederacy of Dunces" by John Kennedy Toole

Related Words

• covert