The exact opposite of bumping uglies. If two ugly people are bumping in the other this two attractive mf-ers having sex in an intense fashion.
Yeah, Tina and Doug were in the closet bumping pretties, good looking motherf------!
bump pretties is when two attractive people have sex. bump uglies is when two unattractive people have sex. (or just people having sex in general)
"i heard James and Ava bump pretties earlier today..."