The woman lays on her back while you start shitting on her torso. Next, you proceed to scoot backwards to her face while saying, "beep beep beep" until you finally rest your ass hole on her mouth. This act should only be reserved for holidays or anniversary's.
"Susie will be pleasantly surprised that in her stocking this Christmas is a gift certificate for one free Pittsburgh Dump Truck."
Keeping with the spirit of the "Three River City", the Pittsburgh Dumptruck occurs when three participants, or "defacateurs" proceed to defecate or "poo" on the chest or upper torso of another participant, willing or non. Said occurance need not occur in or within the vicinity of the City of Pittsburgh.
Dude, that bitch loves a good Pittsburgh Dumptruck, you guys want to drink draft beer all night and shit on her?