- Definitions|2
- Thesaurus|1.5k
- Abbreviations|0
88 entries under solid topic. ×
| tough(adjective, hard, firm, stiff) | |
| unbreakable(adjective, firm, stiff, rigid) | |
| impervious(adjective, set, hard, tough) | |
| compact(adjective, close, set, hard, tough) | |
| unfathomable(adjective, hard, knowledge, obscure, difficult) | |
| incomprehensible(adjective, knowledge, obscure, dark) | |
| dense(adjective, set, hard, tough, firm) | |
| impassable(adjective, dense, unaffected, unyielding) | |
| impermeable(adjective, close, hard, tough) | |
| hard(adjective, tough, firm, cruel) | |
| opaque(adjective, set, heavy, deep) | |
| thick(adjective, dull, close, hard, tough) | |
| arcane(adjective, obscure, strange, doubtful) | |
| firm(adjective, close, set, hard) | |
| unintelligible(adjective, knowledge, obscure, dark) | |
| mysterious(adjective, obscure, strange, secret) | |
| enigmatic(adjective, obscure, difficult, strange) | |
| deep(adjective, set, obscure, heavy) | |
| heavy(adjective, set, hard, tough) | |
| close(adjective, set, hard, tough) |
For more, visit
Impenetrable on
Power Thesaurus
| APA | Smart Define. (2015). impenetrable thesaurus. Retrieved September 21, 2026, from https://smartdefine.org/impenetrable/thesaurus/synonyms |
| Chicago | Smart Define. 2015. "impenetrable thesaurus" https://smartdefine.org/impenetrable/thesaurus/synonyms (accessed September 21, 2026). |
| Harvard | Smart Define 2015, impenetrable thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/impenetrable/thesaurus/synonyms>. |
| MLA | Smart Define. "impenetrable thesaurus" 10 April 2015. Web. 21 September 2026. <https://smartdefine.org/impenetrable/thesaurus/synonyms> |