The act in which the cheeks on the gluteus are fucked in the same way some will compare to "titty-fucking". Spit or some form of lubricant should be used in order to disarray misscomfort.
When one proceeds to make very intense and disgusting slurping and sucking sounds with their tongue and mouth. This is extremely annoying when done close to someone, and has no real use except for when someone is genuinely bored and has nothing else to do.