|a.||1.||Incapable of being penetrated or pierced; not admitting the passage of other bodies; not to be entered; impervious; |
|2.||(Physics) Having the property of preventing any other substance from occupying the same space at the same time.|
|3.||Inaccessible, as to knowledge, reason, sympathy, etc.; unimpressible; not to be moved by arguments or motives; |
|Adj.||1.||impenetrable - not admitting of penetration or passage into or through; "an impenetrable fortress"; "impenetrable rain forests"|
penetrable - admitting of penetration or passage into or through; "a penetrable wall"; "penetrable defenses"
|2.||impenetrable - permitting little if any light to pass through because of denseness of matter; "dense smoke"; "heavy fog"; "impenetrable gloom"|
|3.||impenetrable - impossible to understand; "impenetrable jargon"|