63 entries under underground topic. ×

2
backstairs(sensitive, unknowing, clandestine, undisclosed)
2
clandestine(secret, private, hidden, sneaky)
2
privy(secret, hidden, clandestine, underhanded)
2
sneaky(secret, private, hidden, clandestine)
2
underhanded(secret, hidden, clandestine, sneaky)
1
QT(secret, hidden, unknowing, clandestine)
1
backdoor(sensitive, clandestine, undisclosed, sub-rosa)
1
camouflaged(secret, hidden, clandestine, undisclosed)
1
classified(sensitive, secret, clandestine, undisclosed)
1
close(clandestine, undisclosed)
1
confidential(secret, clandestine, undisclosed, top-secret)
1
conspiratorial(clandestine, undisclosed, sneaky, covert)
1
cryptic(clandestine, undisclosed)
1
discreet(clandestine, undisclosed)
1
dissembled(secret, hidden, clandestine, undisclosed)
1
dissimulated(clandestine, undisclosed)
1
in ambush(expression, sensitive, clandestine, undisclosed)
1
incog(secret, hidden, clandestine, underhanded)
1
incognito(secret, hidden, clandestine, undisclosed)
1
inside(clandestine, undisclosed)
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APASmart Define. (2015). under-the-table thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/under-the-table/thesaurus/synonyms
ChicagoSmart Define. 2015. "under-the-table thesaurus" https://smartdefine.org/under-the-table/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2015, under-the-table thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/under-the-table/thesaurus/synonyms>.
MLASmart Define. "under-the-table thesaurus" 13 April 2015. Web. 25 September 2026. <https://smartdefine.org/under-the-table/thesaurus/synonyms>