under cover

1 of 3

phrase

1

: in an envelope or wrapper

2

: under concealment : in secret

undercover

2 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

3 of 3

noun

: a person engaged in undercover activity : spy

Synonyms of under cover

Adjective

• clandestine
• underground
• covert
• sneak
• private

Noun

• spy
• operative
• agent

Examples of under cover 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

The undercover investigators later spoke with Lorenz by phone. —Rosalio Ahumada, Sacbee.com, 24 Jan. 2026

At the beginning of the season, host Alan Cumming picks the Traitors that will pit the Faithful against each other by murdering them one by one while trying to remain undercover. —Armando Tinoco, Deadline, 24 Jan. 2026

Noun

Le, who was working undercover, was shot while inside his vehicle after responding to one of multiple burglaries at a cannabis business on Embarcadero near Fifth Ave. —Carlos E. Castañeda, CBS News, 11 Dec. 2025

Four other agents accompanied me, all also operating undercover. —Martin Suarez, Rolling Stone, 13 Sep. 2025

Word History

First Known Use

Adjective

1920, in the meaning defined above

Noun

1962, in the meaning defined above

Rhymes for under cover

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

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