Synonyms|558Antonyms|116|Broader|11Narrower|9Related|411

82 entries under expression topic. ×

3
under the breath
3
under the rose
3
with bated breath
2
below ground(adjective, idiom, deep, hidden)
2
in secret
2
sub rosa
2
under cover(secret, spy, covert)
1
Trojan horse
1
black market(noun, idiom, commerce)
1
foundation lace
1
in ambush(idiom, clandestine, undisclosed, concealment)
1
in the recesses(adjective, idiom, covered, oppressed)
1
on the QT(adjective, idiom, obscure, mysterious)
1
on the quiet(idiom, hidden, fraudulent)
1
on the sly(adjective, idiom, unusual, secret)
1
skid block
1
under side
1
vacuum tube
0
Rapid transit
0
avant garde
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APASmart Define. (2015). underground thesaurus. Retrieved September 21, 2026, from https://smartdefine.org/underground/thesaurus/synonyms
ChicagoSmart Define. 2015. "underground thesaurus" https://smartdefine.org/underground/thesaurus/synonyms (accessed September 21, 2026).
HarvardSmart Define 2015, underground thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/underground/thesaurus/synonyms>.
MLASmart Define. "underground thesaurus" 3 November 2015. Web. 21 September 2026. <https://smartdefine.org/underground/thesaurus/synonyms>