In hot-rod groups, short for positrac. Positrac was the GM trade name for a differential gear which would lock under severe loading to ensure that both drive wheels were turning. Highly desired in drag racing. The positrac name is now mostly generic in usage, with many racers referring to every locking diff a "posi".
Watch both tires smoke! You can sure tell that guys running a posi!
posi short for positive hardcore. type of music that is hardcore but postive fast almost punk like in sound but with lyrics that state standing strong and never to give up also things such as if you fuck with me your dead. a term used alot by scene fucks such as my self.
comeback kid is posi as fuck man those guys are hardcore, they will fuck you up if you fuck with them or their freinds.