40 entries under undisclosed topic. ×
| cloak-and-dagger(adjective, obscure, unknown, hidden, clandestine) | |
| underhand(secret, hidden, spy, clandestine, fraudulent) | |
| backstairs | |
| sneaky(adjective, clandestine) | |
| stealthy(adjective, secret, hidden, spy, clandestine) | |
| underhanded(secret, clandestine) | |
| closet(obscure, unknown, hidden, clandestine, fraudulent) | |
| sly | |
| under-the-table(secret, clandestine) | |
| classified(obscure, unknown, clandestine, unrevealed) | |
| confidential(adjective, secret, hidden, spy, clandestine) | |
| in ambush(expression, idiom, clandestine, concealment) | |
| inside | |
| on the QT(expression, adjective, idiom, obscure, mysterious) | |
| ambiguous(obscure, unknown, clandestine, unrevealed) | |
| arcane(obscure, unknown, clandestine, unrevealed) | |
| backdoor(obscure, unknown, clandestine, unrevealed) | |
| camouflaged(obscure, secret, unknown, clandestine) | |
| conspiratorial(obscure, unknown, clandestine, unrevealed) | |
| discreet |
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| APA | Smart Define. (2015). underground thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/underground/thesaurus/synonyms |
| Chicago | Smart Define. 2015. "underground thesaurus" https://smartdefine.org/underground/thesaurus/synonyms (accessed September 25, 2026). |
| Harvard | Smart Define 2015, underground thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/underground/thesaurus/synonyms>. |
| MLA | Smart Define. "underground thesaurus" 3 November 2015. Web. 25 September 2026. <https://smartdefine.org/underground/thesaurus/synonyms> |