A term used to define a particularly large and/or volatile bowel movement. Butt briskets are almost always preceded by several minutes or even hours of intestinal noises. Sometimes the butt brisket is so large that you can actually feel it as it move through your intestines.
When the butt brisket reaches your rectum, it causes the feeling that you are about to uncontrollably shit your pants and forces you to find the nearest toilet, coffee can, bush, etc.
Butt briskets often come out in the form of explosive diarrhea and are sometimes accompanied by jalepeno asshole.
NOTE: not to be confused with butt biscuit
I got a big ol' beefy butt brisket brewing.