Someone who was pissed on as a child. Typically, once a child is urinated on, a plaque (a "Pissbaby Plaque") stating the name of the child, the time and day it was pissed on and by whom is riveted to its back. Pissing on a young child renders them mentally retarded and greasy in complexion.
"Hey Joe, let me see your Pissbaby Plaque! I've gotta see who made you this dumb!"