penetrable

adjective2

1. •
   Capable of being penetrated, entered, or pierced.

   • On the east the high mountain-chain of Zagros, penetrable only in one or two places, forms a barrier of the most marked character, and is beyond a doubt the natural limit for which we are looking. — 1867
2. •
   (figurative) Capable of being fully understood.

   • A Boer may know you, but it will take you some time to know him, and when a certain stage in your acquaintance is reached, you may begin to wonder whether his real nature is penetrable at all. — 1900