Razor Tail
Also known as: razortail
A sharp, worn-down tail (or nose) from constantly scraping it against the ground.
Extended definition
It shows up when the tail gets eaten away from scraping the ground on ollies and tricks, until it's thin as a blade — hence the name. It kills your pop and will literally cut you if you run a hand over it. It's one of the clearest signs a deck is done and it's time for a new one.
Origin / etymology
From "razor": the tail ends up sharpened like one.