A child that results from a sperm donation and is treated as extended family on the part of the sperm donor. In particular, a spuncling is to a spuncle, what a niece or nephew is to an uncle (or aunt). The term is gender neutral.
Dan: Donde esta the tearai, please?
Matt: Huh?
Dan: Where is the baño, kudasai?
Matt: Dude, what the fuck are you saying?
Dan: It's Spanglinese, now where is the damn bathroom?
Matt: Oh...first door on the left.