52 entries under underground topic. ×

16
dark(adjective, dull, obscure, gloomy, lack)
14
obscure(adjective, dull, dark, gloomy, uncertain)
7
ambiguous(adjective, clear, obscure, certain, uncertain)
6
hidden(adjective, secret, unknown, concealed)
4
secret(adjective, unknown, hidden, clandestine)
3
undercover(secret, unknown, hidden, concealed)
2
mysterious(adjective, obscure, dark, secret, private)
2
under wraps(expression, clandestine, undisclosed)
1
camouflaged(obscure, unknown, clandestine, undisclosed)
1
clandestine(secret, unknown, hidden, concealed)
1
enigmatical(obscure, unknown, indefinite, equivocal, clandestine)
1
in ambush(expression, idiom, clandestine, undisclosed)
1
sneaky(uncertain, shaky, unclear, unlikely, questionable)
1
surreptitious(secret, unknown, hidden, concealed)
1
unintelligible(adjective, obscure, uncertain, doubtful, dubious)
0
arcane(obscure, unknown, clandestine, undisclosed)
0
backdoor(obscure, unknown, clandestine, undisclosed)
0
backstairs(clandestine, undisclosed)
0
classified(obscure, unknown, clandestine, undisclosed)
0
cloak-and-dagger(obscure, unknown, clandestine, undisclosed)
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APASmart Define. (2016). clouded thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/clouded/thesaurus/synonyms
ChicagoSmart Define. 2016. "clouded thesaurus" https://smartdefine.org/clouded/thesaurus/synonyms (accessed September 22, 2026).
HarvardSmart Define 2016, clouded thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/clouded/thesaurus/synonyms>.
MLASmart Define. "clouded thesaurus" 29 February 2016. Web. 22 September 2026. <https://smartdefine.org/clouded/thesaurus/synonyms>