The act of having a sexual act "doggy style" and then putting a hollowed out pumpkin on the recipient of the "doggy style". Then once the recipient looks like that sleepy hallow dude, one humps the monster through a wall. Thus the pumpkin chunk.
Browski #1: Dude its halloween are you gonna bone that chick.
Browski #2: Ya bro, im totally gonna be pumpkin chunkin that whore tonight
Browski #3: Poop Dick bro Poop Dick.
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