When diarrhea is violent, it's explosive; An Asspocalypse occurs when Satan himself comes up from the depths of hell, through your colon, and out of your anal orifice in what only can be describe bout of hellish antichrist diarrhea. Explosive is an understatement, and complete loss of consciousness is not uncommon. All it takes is to bring on the asspocalpyse can be as little as one bad burrito from taco bell.
"Did you hear Johnny last night? fuck he had the taco shits!"
"Taco shits? More like asspocalypse."
"I'm not cleaning that shit up"