Adjective: impenetrable im'pe-ni-tru-bul
- Not admitting of penetration or passage into or through
"an impenetrable fortress"; "impenetrable rain forests"
- Permitting little if any light to pass through because of denseness of matter
"impenetrable gloom";
- dense, heavy
- Impossible to understand
"impenetrable jargon"
See also: dense, incomprehensible, thick, uncomprehensible
Antonym: penetrable
Encyclopedia: Impenetrable