形容词
1. 不能穿过的;刺不进的;透不过的
If you describe something such as a barrier or a forest as impenetrable, you mean that it is impossible or very difficult to get through.
2. 费解的;难以理解的
If you describe something such as a book or a theory as impenetrable, you are emphasizing that it is impossible or very difficult to understand.
1. impossible to understand
e.g. impenetrable jargon
2. not admitting of penetration or passage into or through
e.g. an impenetrable fortress
impenetrable rain forests
3. permitting little if any light to pass through because of denseness of matter
e.g. dense smoke
heavy fog
impenetrable gloom