A social gathering at which feces/defication fetishes are enjoyed. Any gathering in which the focus involves the spreading, projection, or excessive use of bodily fluids for fetish satisfying purposes. Often refers to group parties at which individuals lay under a glass table while others deficate on the glass above them (aka glass bottom boating), though may be more specific to the observance of more explosive diarrhea in this context.
May also refer to gory horror/slasher movie marathons or group viewings.
Jaime got to observe his first glass bottom boating at the splatter party last weekend.