1.) a hot chick. When you are with your friends and you see a hot chick, you say, yell, whisper (whatever the situation) 'hairpie' to get your friends attention. They will then give their approval or disapproval of your observation with a nay or yay.
Two dudes walking in the store...........
Dude #1: What did you do last night?
Dude #2: I cranked it to some new skeeze. Pretty good stuff. Hey have you ever,(hot chick walks by, dude stops in mid-conversation), Hairpie!
Dude #1: Definitely a Hairpie.