Synonyms of impenetrability

2 Syllables
thickness, body, tightness, firmness
3 Syllables
density, concretion, heaviness, quantity, densities, compactness, closeness, fixedness, denseness, crowdedness, frequency
4 Syllables
consistency, solidity, massiveness
5 Syllables
substantiality, impliability
6 Syllables
impermeability, inelasticity