Shapoppin' is a phrase used when someone is feeling themselves. They use it to mean they are looking flawless at the moment.

when you're hungover as shit after a spending a night drunk as a skunk

shapoppin'- something is popping, amazing or outstanding.

It's a word that getto people use...as you can see and the getto people use it when they get ready to fight

A hood girl that is pretty but also sassy and does not care what anyone says and does her own thing cause she’s shapoppin