A Princeton Blumpy is when someone (person A) performs oral sex on someone else (person B) who is having a bowel movement and there is someone (person C) who is getting "pooped" on (usually the face). However, half way through this act, person C will slowly move their face up to the sphincter of person B until they eventually reach the sphincter and then "cork it"(stopping the further flow of feces by blocking the sphincter with the tongue).
However, if the person's tongue can not hold the pressure of the flow of feces and they pull away their tongue, the fecal matter that escapes in this "explosion" is known as "The Koprek Kannon"
Roger: "Well, we tried out The Princeton Blumpy"
Steve:"oh...did the kannon happen?"