adj. 25B6; adjective SECRET, covert, furtive, surreptitious, stealthy, cloak-and-dagger, hole-and-corner, closet, backstairs, hugger-mugger; informal hush-hush.
CLANDESTINE
Meaning of CLANDESTINE in English
Concise Oxford thesaurus English vocabulary. Краткий оксфордский словарь английского языка тезаурус. 2012