| impenetrability | (n) the quality of being impenetrable (by people or light or missiles etc.), Syn. imperviousness, Ant. penetrability, perviousness |
| penetrability | (n) the quality of being penetrable (by people or light or missiles etc.), Syn. perviousness, Ant. imperviousness, impenetrability |
| Perviousness | n. The quality or state of being pervious; |