50 entries under underground topic. ×
| sneaky(clandestine, undisclosed) | |
| stealthy(clandestine, undisclosed) | |
| top-secret(clandestine, undisclosed) | |
| top secret(expression, clandestine, undisclosed) | |
| under-the-table(clandestine, undisclosed) | |
| under false pretense(expression, idiom, clandestine, undisclosed) | |
| underhand(clandestine, undisclosed) | |
| underhanded(clandestine, undisclosed) | |
| unenlightened(obscure, clandestine, undisclosed, unrevealed) | |
| unfrequented(obscure, clandestine, undisclosed, unrevealed) |
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| APA | Smart Define. (2015). unknown thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/unknown/thesaurus/synonyms |
| Chicago | Smart Define. 2015. "unknown thesaurus" https://smartdefine.org/unknown/thesaurus/synonyms (accessed September 22, 2026). |
| Harvard | Smart Define 2015, unknown thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/unknown/thesaurus/synonyms>. |
| MLA | Smart Define. "unknown thesaurus" 10 April 2015. Web. 22 September 2026. <https://smartdefine.org/unknown/thesaurus/synonyms> |