1. Not admitting of penetration or passage into or through
   "an impenetrable fortress"; "impenetrable rain forests" 
2. Permitting little if any light to pass through because of denseness of matter
   "impenetrable gloom"
   - dense, heavy 
3. Impossible to understand
   "impenetrable jargon"

See also: dense, impenetrability, impenetrableness, incomprehensible, thick, uncomprehensible

Antonym: penetrable

Encyclopedia: Impenetrable

• wilfulness
• Wilhelm Apollinaris de Kostrowitzki
• Wilhelm Eduard Weber
• Wilhelm Grimm
• Wilhelm II
• Wilhelm Karl Grimm
• Wilhelm Konrad Roentgen
• Wilhelm Konrad Röntgen
• Wilhelm Ostwald
• Wilhelm Reich
• Wilhelm Richard Wagner
• Wilhelm von Opel
• wiliness
• Wilkes
• Wilkes Land
• Wilkie Collins
• Wilkins
• Wilkins Micawber
• Wilkinson
• will
• Will Durant
• Will Hays
• Will Keith Kellog
• Will Rogers
• will-o'-the-wisp