51 entries under underground topic. ×

20
close(adjective, quiet, soft, low, restrained)
16
secret(adjective, quiet, mean, smooth, obscure)
15
reticent(adjective, close, quiet, soft, low)
5
hidden(adjective, quiet, obscure, plain, strange)
4
dark(adjective, close, strange, reticent, clandestine)
4
discreet(adjective, close, quiet, soft, low)
3
confidential(adjective, restricted, clandestine, discreet)
3
mysterious(adjective, strange, secret, private, reticent)
3
retired(adjective, quiet, humble, distant, minor)
2
classified(clandestine, undisclosed)
2
enigmatical(adjective, strange, clandestine, undisclosed)
2
hush-hush(adjective, quiet, dishonest, cunning, deceitful)
2
secluded(adjective, quiet, humble, distant, minor)
1
abstruse(strange, unknown, clandestine, curious)
1
arcane(strange, clandestine, undisclosed, inexplicable)
1
backdoor(clandestine, undisclosed)
1
conspiratorial(adjective, clandestine, undisclosed, sneaky)
1
covered(clandestine, undisclosed)
1
disguised(adjective, clandestine, undisclosed, sneaky)
1
dissembled(restricted, clandestine, discreet, undisclosed)
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APASmart Define. (2015). secretive thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/secretive/thesaurus/synonyms
ChicagoSmart Define. 2015. "secretive thesaurus" https://smartdefine.org/secretive/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2015, secretive thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/secretive/thesaurus/synonyms>.
MLASmart Define. "secretive thesaurus" 14 April 2015. Web. 25 September 2026. <https://smartdefine.org/secretive/thesaurus/synonyms>