Adjective

• S: (adj) impenetrable (not admitting of penetration or passage into or through) "an impenetrable fortress"; "impenetrable rain forests"
• S: (adj) dense, heavy, impenetrable (permitting little if any light to pass through because of denseness of matter) "dense smoke"; "heavy fog"; "impenetrable gloom"
• similar to
• derivationally related form
• antonym
• W: (adj) thin [Indirect via thick] (relatively thin in consistency or low in density; not viscous) "air is thin at high altitudes"; "a thin soup"; "skimmed milk is much thinner than whole milk"; "thin oil"
• S: (adj) impenetrable (impossible to understand) "impenetrable jargon"