A Crustin is a kid who wears the same sweater everyday, often with a mismatched Yankees cap, maybe even a women's one. He also probably sports a classic bowl cut and listens to poser music, like Lil Wayne. A crustin is also said to have very little athletic talent or athelticism, but often tries as hard as he can.
Kid A: who's that kid in the yankees cap listening to lil wayne?
B: whatta crustin