70 entries under underground topic. ×

2
top secret(expression, adjective, secret, private, hidden)
2
under wraps(expression, secret, clandestine, undisclosed)
2
undisclosed
2
unrevealed(clandestine, undisclosed)
1
backstairs(clandestine, discreet, undisclosed)
1
dissembled(clandestine, discreet, undisclosed)
1
dissimulated(clandestine, discreet, undisclosed)
1
in ambush(expression, clandestine, discreet, undisclosed)
1
obscure(clandestine, undisclosed, provisional, restrictive)
1
secretive(clandestine, discreet, undisclosed)
1
sneak(clandestine, discreet, undisclosed)
1
sub-rosa(secret, clandestine, undisclosed, top-secret)
1
under-the-table(secret, clandestine, undisclosed, top-secret)
0
abstruse(modern, advanced, clandestine, undisclosed)
0
ambiguous(adjective, clandestine, undisclosed, surreptitious)
0
backdoor(clandestine, undisclosed)
0
camouflaged(clandestine, undisclosed)
0
cloak-and-dagger(secret, clandestine, undisclosed, top-secret)
0
closet(secret, clandestine, undisclosed, confidential)
0
clouded(clandestine, undisclosed)
10 years ago|28k views|share |citing 
APASmart Define. (2016). restricted thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/restricted/thesaurus/synonyms
ChicagoSmart Define. 2016. "restricted thesaurus" https://smartdefine.org/restricted/thesaurus/synonyms (accessed September 23, 2026).
HarvardSmart Define 2016, restricted thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/restricted/thesaurus/synonyms>.
MLASmart Define. "restricted thesaurus" 26 February 2016. Web. 23 September 2026. <https://smartdefine.org/restricted/thesaurus/synonyms>