: capable of being penetrated.

What is not penetrable?

not penetrable; that cannot be penetrated, pierced, entered, etc. inaccessible to ideas, influences, etc. incapable of being understood; inscrutable; unfathomable: an impenetrable mystery.

Is Penetrability a word?

penetrability - the quality of being penetrable (by people or light or missiles etc.) impenetrability, imperviousness - the quality of being impenetrable (by people or light or missiles etc.)