adj. 25B6; adjective COVERT, secret, clandestine, underground, surreptitious, furtive, cloak-and-dagger, hole-and-corner, hugger-mugger, stealthy, hidden, concealed; informal hush-hush, sneaky.
overt.
UNDERCOVER
Meaning of UNDERCOVER in English
Concise Oxford thesaurus English vocabulary. Краткий оксфордский словарь английского языка тезаурус. 2012