Pronunciation: [ klan-des-tin ]
Definition: adjective
characterized by, done in, or executed with secrecy or concealment, especially for purposes of subversion or deception; private or surreptitious

Origin: Mid 16th century; Latin
Etymology: from French clandestin or Latin clandestinus, from clam ‘secretly’
Usage:

Synonyms:
covert
fraudulent
furtive
hidden
hush-hush
illicit
surreptitious
underground
Antonyms:
aboveboard
authorized
public
known
open
Example: The club's clandestine meetings went on for two years before they got caught.