53 entries under underground topic. ×

40
obscure(adjective, hard, solid, dark, strange)
36
cryptic(adjective, knowledge, evil, obscure, dark)
29
mystical(adjective, hard, knowledge, evil, obscure)
28
arcane(adjective, knowledge, evil, obscure, solid)
26
occult(noun, adjective, knowledge, evil, obscure)
25
dark(adjective, obscure, hidden, secret, strange)
24
mystic(adjective, knowledge, evil, obscure, solid)
24
recondite(adjective, evil, obscure, dark, strange)
23
abstruse(noun, adjective, hard, evil, obscure)
20
esoteric(adjective, hard, evil, obscure, dark)
18
secret(adjective, quiet, evil, obscure, dark)
13
deep(adjective, hard, evil, obscure, heavy)
11
hidden(adjective, hard, evil, obscure, solid)
11
ambiguous(adjective, obscure, dark, uncertain, doubtful)
7
unintelligible(adjective, hard, obscure, solid, dark)
3
classified(obscure, unknown, clandestine, undisclosed)
3
secretive(adjective, strange, secret, private, reticent)
2
clouded(adjective, obscure, dark, secret, private)
2
hush-hush(quiet, clandestine, undisclosed, intriguing)
2
restricted(clandestine, undisclosed)
<123>
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APASmart Define. (2016). mysterious thesaurus. Retrieved September 27, 2026, from https://smartdefine.org/mysterious/thesaurus/synonyms
ChicagoSmart Define. 2016. "mysterious thesaurus" https://smartdefine.org/mysterious/thesaurus/synonyms (accessed September 27, 2026).
HarvardSmart Define 2016, mysterious thesaurus, Smart Define, viewed 27 September, 2026, <https://smartdefine.org/mysterious/thesaurus/synonyms>.
MLASmart Define. "mysterious thesaurus" 24 February 2016. Web. 27 September 2026. <https://smartdefine.org/mysterious/thesaurus/synonyms>