A permit fag is someone who has recently received their driving permit or hasn't gotten their license yet, and constantly talks about how good of a driver they are, or corrects mistakes that a licensed driver makes. They constantly recite terms and rules that they have just recently learned in a Drivers Education course. Overall they are just conceited little high-schoolers who seem to think they are driving experts. Often times they actually aren't good drivers at all, and passengers tend to spend most of the car ride grabbing the "oh shit handles".
Permit Fag: "Yeah I'm such a good driver. I haven't even gotten a ticket yet or anything."
Guy: "Shut the fuck up. You've had your permit for two days, you conceited piece of shit."