Impervious

Part of speech: adjective (a.)

Not pervious; not admitting of entrance or passage through; as, a substance impervious to water or air. This gulf impassable, impervious. Milton. The minds of these zealots were absolutely impervious. Macaulay.

Synonyms: Impassable; pathless; impenetrable; imperviable; impermeable. Im*per"vi*ous*ly, adv. Im*per"vi*ous*ness, n.