That cannot be penetrated or pierced; not admitting the passage of other bodies; as an impenetrable — shield.

Not to be affected or moved; not admitting impressions on the mind. The hardened sinner remains impenetrable to the admonitions of the gospel.

Not to be entered by the sight; as impenetrable darkness. Hence,

Not to be entered and viewed by the eye of the intellect; as impenetrable obscurity or abstruseness.