undercover

1 undertaken or done so as to escape being observed or known by others an undercover operation to infiltrate the terrorist organization Synonyms backstairs, behind-the-scenes, clandestine, covert, furtive, hole-and-corner, hugger-mugger, hush-hush, private, privy, sneak, sneaking, sneaky, stealth, stealthy, surreptitious, secret, underground, underhand, underhandedRelated Words back-channel, closed-door, off-the-books, off-the-record; classified, confidential, restricted, top secret, undisclosed; concealed, hidden, secreted, subterranean, unadvertised, unexposedNear Antonyms acknowledged, avowed; aboveboard, straightforward, unconcealed, undisguised; unclassified, unrestricted; clear, evident, manifest, obvious, patent, plainAntonyms open, overt, public

2 working on missions in which one's objectives, activities, or true identity are not publicly revealed for months she's been an undercover agent pretending to be a drug dealer Synonyms secretRelated Words covert, private, secretive, subterraneanNear Antonyms overt