impenetrable

Adjective

• impossible to understand
  • impenetrable jargon
    

• permitting little if any light to pass through because of denseness of matter
  • dense smoke
    
  • heavy fog
    
  • impenetrable gloom
    

• not admitting of penetration or passage into or through
  • an impenetrable fortress
    
  • impenetrable rain forests
    

Related words

• Synonyms: 
  dense , heavy