A spianal tap occurs when the aggressor's penis is so large relative to the orifice being fucked it actually rips through protective tissues lining the spine and makes contact with the nerve tissue within the spine itself, resulting in a rush of simultaneous pain and pleasure for the victim/beneficiary. As this sexual position carries potential health risks it is typically reserved for safe locations such as hospitals where emergency care can be given immediately after said act.
Big pimpin with da one and only g dizzle all up in herre in da big WA!! Spianal Tap nigga!!