The condition of the urgent need of a toilet because of upcoming mass defecation. The large intestine usually builds in gas pressure repeatedly, then fortunately subsides as you drive around looking for the best fast food restaurant to rush the restroom. As you park, the inevitable last build throws you from the car, you burst into a stall, and you barely drop your pants in time before the assplosion occurs. If your ass does not create a seal with the seat, the assplosion produces colorful feces all around the stall including walls, toilet, floor, and sometimes ceiling. Strangely, the toilet paper is untouched so you are able to make a clean getaway and vow never to return to that establishment. It makes for a good story every time you pass another similar restaurant.

extemely wet, violently forceful diarrhea, which explodes from from the anus in one awesome deluge.

The art of projectile-style defecation. The end result is a messy, steamy, smelly possible smoke filled (we don't get it either) bathroom who's cleaning requires at least a firehose and a bucket of bleach.
Assplosions have been known to inexplicably end up on the underside of the toilet seat.

In ancient China, those capable of the assplosion were looked upon with the highest regard.

see also BM Blowout

An extreme case of diarrhea where very runny feces is excreted unvoluntarily from the anus at inconcievable speeds.

The act of imploding into one's self, then promptly exploding that out of the anus.

The anal explosion that occurs after one eats mexican food, particularly, Taco Bell.

When you fart so hard your arse hurts and you get a headache and shit your dacks and basically make everything around you smell like crap!