Refers to the aesthetic features and overall appearance of someone's posterior. These details can vary widely depending on how a particular observer views various attributes in the context of attractiveness/desirability --- where one person
may prefer a
small firm tight
bum as being more ideal for spanking and/or settling on one's lap, someone else might druther a bigger floppier pair of butt-
cheeks which are more pleasurable/satisfying to squeeze and knead, especially if the massager himself possesses large hands that he enjoys having "filled".
I don't worry about asspects too much when I
date a new lady... to me, if she's got a
sweet placid face and a nice personality, I could really care less what her butt or tits look
like.