UNDERCOVER

clandestine, cloak-and-dagger, hole-and-corner, hugger-mugger, hush-hush, secret, surreptitious, undercover, underground

(adjective) conducted with or marked by hidden aims or methods; “clandestine intelligence operations”; “cloak-and-dagger activities behind enemy lines”; “hole-and-corner intrigue”; “secret missions”; “a secret agent”; “secret sales of arms”; “surreptitious mobilization of troops”; “an undercover investigation”; “underground resistance”

Source: WordNet® 3.1

Etymology

Adjective

undercover (comparative more undercover, superlative most undercover)

Performed or happening in secret.

Employed or engaged in spying or secret investigation.

Synonyms

• clandestine

• See also covert

Noun

undercover (plural undercovers)

A person who works undercover.

Verb

undercover (third-person singular simple present undercovers, present participle undercovering, simple past and past participle undercovered)

To provide too little coverage.

Source: Wiktionary