71 entries under adjective topic. ×

5
deep(obscure, down, unknown, far)
5
secluded(obscure, secret, unknown, hidden)
5
under wraps(expression, idiom, secret, hidden)
4
belowground
4
experimental(secret, subversive)
4
irregular
4
mysterious(obscure, secret, unknown, hidden)
4
privy
4
radical(secret, subversive)
4
sneaky(clandestine, undisclosed)
4
stealthy(secret, hidden, spy, clandestine)
4
sunken
4
underfoot
3
subversive(destructive, rebellious)
2
below ground(expression, idiom, deep, hidden)
2
disorderly
2
mystic(obscure, secret, unknown, hidden)
2
mystical(obscure, secret, unknown, hidden)
2
obscured(secret, hidden, clandestine, concealed)
2
subterrestrial
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APASmart Define. (2015). underground thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/underground/thesaurus/synonyms
ChicagoSmart Define. 2015. "underground thesaurus" https://smartdefine.org/underground/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2015, underground thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/underground/thesaurus/synonyms>.
MLASmart Define. "underground thesaurus" 3 November 2015. Web. 25 September 2026. <https://smartdefine.org/underground/thesaurus/synonyms>