- Definitions|2
- Thesaurus|1.5k
- Abbreviations|0
88 entries under solid topic. ×
| inexplicable(adjective, obscure, dark, strange) | |
| mystic(adjective, obscure, dark, superior) | |
| tight(adjective, close, short, substantial) | |
| condensed(adjective, set, hard, tough) | |
| murky(adjective, obscure, dark, gloomy) | |
| unknowable(adjective, obscure, dark, superior) | |
| compressed(adjective, set, hard, tough, firm) | |
| unaccountable(adjective, obscure, strange, doubtful) | |
| baffling(adjective, obscure, deep, mysterious) | |
| hidden(adjective, obscure, difficult, dark) | |
| nonporous(hard, rigid, resistant, impervious) | |
| packed(adjective, close, set, hard, firm) | |
| substantial(adjective, close, set, strong, hard) | |
| unyielding(adjective, set, hard, tough, firm) | |
| cabalistic(adjective, obscure, strange, odd) | |
| concrete(adjective, set, hard, tough) | |
| crowded(adjective, close, set, heavy) | |
| enigmatical(adjective, strange, supernatural, dense) | |
| inflexible(adjective, set, strong, hard, tough) | |
| rigid(adjective, set, strong, hard, tough) |
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| APA | Smart Define. (2015). impenetrable thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/impenetrable/thesaurus/synonyms |
| Chicago | Smart Define. 2015. "impenetrable thesaurus" https://smartdefine.org/impenetrable/thesaurus/synonyms (accessed September 23, 2026). |
| Harvard | Smart Define 2015, impenetrable thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/impenetrable/thesaurus/synonyms>. |
| MLA | Smart Define. "impenetrable thesaurus" 10 April 2015. Web. 23 September 2026. <https://smartdefine.org/impenetrable/thesaurus/synonyms> |