- not admitting of penetration or passage into or through; "an impenetrable fortress"; "impenetrable rain forests"
- dense: permitting little if any light to pass through because of denseness of matter; "dense smoke"; "heavy fog"; "impenetrable gloom"
- impossible to understand; "impenetrable jargon"
- (impenetrableness) impenetrability: incomprehensibility by virtue of being too dense to understand
- In metaphysics, impenetrability is the name given to that quality of matter whereby two bodies cannot occupy the same space at the same time. ...
- not penetrable; incomprehensible; inscrutable
- Inaccessible. See Phase Impenetrability Condition.
- Term applied historically to the area of the dry chaco with the most inhospitable conditions for white settlement, due to lack of water; the name of a zone of northwestern Chaco Province.
- incapable of being penetrated
- Unable to pass, blocked