60 entries under underground topic. ×

1
sneaky(clandestine, undisclosed)
1
stealthy(adjective, clandestine, undisclosed)
1
sub-rosa(close, clandestine, undisclosed, furtive)
1
surreptitious(clandestine, undisclosed)
1
top secret(expression, close, private, clandestine)
1
unacknowledged(close, clandestine, undisclosed, furtive)
1
under-the-table(clandestine, undisclosed)
1
under false pretense(expression, idiom, close, clandestine)
0
abstruse(clandestine, undisclosed)
0
ambiguous(clandestine, undisclosed)
0
arcane(intimate, secret, private, clandestine)
0
cloak-and-dagger(clandestine, undisclosed)
0
clouded(clandestine, undisclosed)
0
conspiratorial(clandestine, undisclosed)
0
covered(clandestine, undisclosed)
0
enigmatical(clandestine, undisclosed)
0
mystic(clandestine, undisclosed)
0
mystical(clandestine, undisclosed)
0
obscure(clandestine, undisclosed)
0
occult(clandestine, undisclosed)
11 years ago|17k views|share |citing 
APASmart Define. (2015). inside thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/inside/thesaurus/synonyms
ChicagoSmart Define. 2015. "inside thesaurus" https://smartdefine.org/inside/thesaurus/synonyms (accessed September 22, 2026).
HarvardSmart Define 2015, inside thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/inside/thesaurus/synonyms>.
MLASmart Define. "inside thesaurus" 10 April 2015. Web. 22 September 2026. <https://smartdefine.org/inside/thesaurus/synonyms>