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

76 entries under idiom topic. ×

3
under the rose
3
with bated breath
2
below ground(expression, adjective, deep, hidden)
2
in secret
2
sub rosa
1
black market(noun, expression, commerce)
1
foundation lace
1
in ambush(expression, clandestine, undisclosed, concealment)
1
in the recesses(expression, adjective, covered, oppressed)
1
on the QT(expression, adjective, obscure, mysterious)
1
on the quiet(expression, hidden, fraudulent)
1
on the sly(expression, adjective, unusual, secret)
1
skid block
1
under side
1
vacuum tube
0
Rapid transit
0
behind a screen(expression, concealment)
0
below grade
0
bottom panel
0
bottom plating
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APASmart Define. (2015). underground thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/underground/thesaurus/synonyms
ChicagoSmart Define. 2015. "underground thesaurus" https://smartdefine.org/underground/thesaurus/synonyms (accessed September 24, 2026).
HarvardSmart Define 2015, underground thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/underground/thesaurus/synonyms>.
MLASmart Define. "underground thesaurus" 3 November 2015. Web. 24 September 2026. <https://smartdefine.org/underground/thesaurus/synonyms>