71 entries under adjective topic. ×
| clandestine(secret, unknown, hidden, sly) | |
| secret(unknown, hidden, spy, concealed) | |
| buried(verb, secret, unknown, hidden) | |
| covert(secret, unknown, hidden, concealed) | |
| surreptitious(secret, unknown, hidden, concealed) | |
| undercover(secret, unknown, hidden, spy) | |
| subterranean(surface, depth) | |
| covered(obscure, unknown, hidden, concealed) | |
| hidden(verb, secret, unknown, concealed) | |
| concealed(secret, unknown, hidden, spy) | |
| hole-and-corner(secret, hidden, spy, covert) | |
| cloak-and-dagger(obscure, unknown, hidden, clandestine) | |
| furtive(obscure, secret, unknown, hidden) | |
| hush-hush(secret, hidden, spy, clandestine) | |
| hugger-mugger | |
| alternative(secret, secretive, subversive, dissident) | |
| avant-garde(secret, secretive, subversive, dissident) | |
| private(obscure, secret, unknown, hidden) | |
| revolutionary(secret, subversive) | |
| subterraneous |
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| APA | Smart Define. (2015). underground thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/underground/thesaurus/synonyms |
| Chicago | Smart Define. 2015. "underground thesaurus" https://smartdefine.org/underground/thesaurus/synonyms (accessed September 22, 2026). |
| Harvard | Smart Define 2015, underground thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/underground/thesaurus/synonyms>. |
| MLA | Smart Define. "underground thesaurus" 3 November 2015. Web. 22 September 2026. <https://smartdefine.org/underground/thesaurus/synonyms> |