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

Horrified by the secrets revealed by Bateman, Christine Marie and Katas were emboldened to go undercover as amateur sleuths. —Liam Quinn, PEOPLE, 9 Apr. 2026

The arrest follows an undercover investigation by CNN into online networks of men teaching each other how to drug and rape their partners. —Saskya Vandoorne, CNN Money, 9 Apr. 2026

Noun

Meanwhile, Chee goes further undercover. —Jordan Hoffman, Entertainment Weekly, 16 Mar. 2026

Sources close to production reveal his character is working undercover. —Rosy Cordero, Deadline, 10 Feb. 2026

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