ass geyser
When you have not gone to the bathroom in a few days and really have to go and as soon as you pull down your pants your shit comes out and splatters everywhere like a geyser.
(in a public bathroom) "Woah, why is there shit all over the walls?"
"The guy who just walked out had the biggest ass geyser I've ever seen"
"The guy who just walked out had the biggest ass geyser I've ever seen"