Nasty bitches are known for their extremely disgusting properties and abilities. They are the most repulsive type of women out there, usually robustly overweight along with many other gross attributes. If I had to describe them in a word or two I'd say: Pure Filth.
Johnny: So Dillon I heard you like fucken NASTY ass bitches.
Dillon: Fucken A' my nigga, the nastier the better... they're easy game, man. In fact, I'm dating a nasty bitch named Tiffany and she's 575 lbs. of FREAK!
Johnny: You really are a nasty mother fucker...