Here's a breakdown:
* Impossible to pass through: This refers to something that is physically solid or dense, preventing anything from getting through. Think of a thick forest, a stone wall, or a layer of ice.
* Impossible to understand: This applies to concepts, language, or situations that are very complex, confusing, or unclear.
Examples:
* Physical: "The jungle was impenetrable, with vines and thorns blocking every path."
* Conceptual: "The professor's lecture was impenetrable, filled with technical jargon and abstract ideas."
Similar words:
* Opaque
* Inaccessible
* Inscrutable
* Unfathomable
* Indecipherable