1. to leave, to store ("leave something somewhere for shelter", for instance a box of clothes at a friend's while you're subletting your apartment)
2. to take shelter ("sich+Acc unterstellen", in context of rain or storm)
"unterstellen" is both, separable and non-separable. Today, we'll learn which will help you against rain and which is generally not nice. Also: runterstellen.
Vocab:
unterstellen, sich unterstellen, die Unterstellung