- Definitions|2
- Thesaurus|1.5k
- Abbreviations|0
308 entries under adjective topic. ×
| unbeatable | |
| unknowable(obscure, solid, dark, superior) | |
| abstruse(obscure, difficult, strange, deep) | |
| cloudy(dark, gloomy, dense, misty) | |
| compressed(set, hard, tough, firm) | |
| hazy | |
| perplexing | |
| puzzling(obscure, strange, sophisticated, complicated) | |
| rocky(set, firm, stiff, compact) | |
| steely(firm, rigid, unyielding) | |
| unaccountable(obscure, solid, strange, doubtful) | |
| adamant(firm, rigid, unyielding, steely) | |
| baffling(obscure, solid, deep, mysterious) | |
| cryptic(obscure, strange, sophisticated, complicated) | |
| dark(feature, obscure, mysterious, hidden) | |
| hidden(obscure, difficult, solid, dark) | |
| immune(unaffected, unyielding, unbending, resistant) | |
| incognizable(incomprehensible, unintelligibility) | |
| packed(close, set, hard, firm) | |
| proof |
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| APA | Smart Define. (2015). impenetrable thesaurus. Retrieved September 26, 2026, from https://smartdefine.org/impenetrable/thesaurus/synonyms |
| Chicago | Smart Define. 2015. "impenetrable thesaurus" https://smartdefine.org/impenetrable/thesaurus/synonyms (accessed September 26, 2026). |
| Harvard | Smart Define 2015, impenetrable thesaurus, Smart Define, viewed 26 September, 2026, <https://smartdefine.org/impenetrable/thesaurus/synonyms>. |
| MLA | Smart Define. "impenetrable thesaurus" 10 April 2015. Web. 26 September 2026. <https://smartdefine.org/impenetrable/thesaurus/synonyms> |