look up any word, like trill:
 
1.
"Tassnim" is a word commonly used to describe the best roommate one has ever had.

It can also describe one who is extremely attractive, but spends entirely too much time studying.
Mahtab: Oh man, that is one big pile of dishes
Mahtab's Roommate: No worries, I'll do them.
Mahtab: That's so tassnim! Thanks!
by plastic_pigeon February 06, 2010