- Difficult to understand
- Esoteric
- Stubs are complicated and hard to understand
- Concealed or hidden out of the way.
- Remote from apprehension; difficult to be comprehended or
understood; recondite; as, abstruse learning.
- ... or outer
- Esoteric
- Hidden
- Hidden (feelings)
- Inside
- Inside beginners
- Inside part
- Esoteric; lofty
- Less dense than normal
- of Rarefy