A "Rectum Apocalypse" occurs when Satan emerges from ones anus to destroy the world. You can also describe an extroardinarily large dump as a rectum apocalypse, or an anal armageddon.
Teacher: "Billy, I told you that you had 3 minutes in the bathroom! You're 30 minutes late!"
Billy: "Sorry, Teach! I had the rectum apocalypse!"
Billy: "Sorry, Teach! I had the rectum apocalypse!"
by Matt Bonn October 4, 2006