undercover

1 of 3

adjective

un·​der·​cov·​er ˌən-dər-ˈkə-vər 

: acting or executed in secret

specifically : employed or engaged in spying or secret investigation

an undercover agent

undercover adverb

undercover

2 of 3

noun

: a person engaged in undercover activity : spy

under cover

3 of 3

phrase

1

: in an envelope or wrapper

2

: under concealment : in secret

Synonyms of undercover

Adjective

• clandestine
• underground
• covert
• sneak
• private

Noun

• spy
• operative
• agent

Examples of undercover in a Sentence

Adjective

an undercover operation to infiltrate the terrorist organization

for months she's been an undercover agent pretending to be a drug dealer

Noun

within the city was a well-organized fifth column, and these undercovers would make themselves known as soon as the invading forces breached the city limits

Recent Examples on the Web

Adjective

And a special shoutout to Jed York, the 49ers owner who was recently in the news after his arrest for allegedly trying to pay $160 to an undercover officer who was posing as a prostitute. — Jon Greenberg, New York Times, 9 Sep. 2026

Police then began an undercover investigation of Conahan and later arrested him on murder charges for Montgomery’s killing. — Amanda Lee Myers, USA Today, 9 Sep. 2026

Noun

Steinem spent 11 days working undercover as a bunny in Manhattan's Playboy Club and documenting her experience. — Jennifer Hassan, USA Today, 3 Sep. 2026

Federal prosecutors accused Heidi Beirich, an expert on political extremism and a former director of the nonprofit’s intelligence project, of overseeing payments to informants working undercover in a variety of hate groups. — Jeremy Roebuck, Washington Post, 12 Aug. 2026

Phrase

Other soccer-like traits at Ryan Field include a very high proportion of the seats being under cover and the striking sight that what Americans across the land have come to know as the Upper Deck experience just does not exist here. — The Editorial Board, Chicago Tribune, 6 Sep. 2026

That same teen sensation left West Africa due to troubles from its dictatorship, and moved to Paris under cover of night and a clandestine air flight. — A.d. Amorosi, Variety, 18 Aug. 2026

Word History

First Known Use

Adjective

1920, in the meaning defined above

Noun

1962, in the meaning defined above

Rhymes for undercover

• rediscover
• cover
• hover
• plover
• discover
• hardcover
• recover
• thereover
• uncover

Kids Definition

undercover

adjective

un·​der·​cov·​er

-ˌkəv-ər

: acting or performed in secret

an undercover scheme

especially : employed or engaged in spying or secret investigation

an undercover agent

undercover adverb