Slam dump
The immediate release of poop as soon as you sit on the toilet after holding it in for a while or after eating too much. Just like a slam dunk, only done with the ass.

Having to take a shit real bad
I went to go eat with a friend the other day. When we go back to the dorm he scurried to the bathroom, taking small but quick steps. Seconds after he shut the door I heard him shout "slam dump!"