This is the term describing the act involving one sick person and a (preferably) dead ape. This act requires the insertion of the penis into the nasal cavity of the ape and ejaculating as close to the brain of the ape as possible. If this position is achieved and semen reaches the brain, the ape will react as if it has been shot by a cannon, recoiling its head backwards. If it is alive of course. If not, you are a sick zoonecrophiliac.
"Guys, I'm gonna go do a Simian Cranial Cannon, be back in 5."
"Ok Peter, make sure its dead this time, unlike last time, OK?"