A beauty supply is a store where people (usually females) go out and buy beauty supplys, see thats why its called a beauty supply!! :)(smile)! the "supply"s usually consist of hair products; such as hair gel (see pro-style gel, or scrunchies, or brushes, combs etc... Or you can even buy hair weaves for braids or regular full head weaves. Or you can buy make-up, nail polish, or almost any thing else you can think of. Some of them even sell clothing. (usually only the more urban ones, like ones in urban cities, like oakland, or atlanta, or places like that).
Girl 2: Oh, girl at the BEAUTY SUPPLY on 23st.,you know the one across the street form the nail shop.
Girl 1: Ooh, imma have ta go get me some, how much was it?
Girl 2: Only $10. & if u want ur hair braided, they got that kind of hair on sale for 2 for $5.
Girl 1: Ooh, 4-real, HEY!!, let me call my cousin ra ra and see if she could braid my hair!