1. an unusually large wave or splash produced in a toilet bowl by a large or well-placed excrement (poo).
2. an exceptionally large, oderiferous or much-anticipated bowel movement.
Origin:
2011-2012; < Brinston, Ontario, Canada. Based on Japanese word "tsunami", equivalent to tsu harbor (earlier tu ) + nami wave < poo (poo) + nami (wave).
A turd so powerful and big that you are sure it is going to make a huge splash, but instead it enters the water smoothly and makes almost no splash, just like an Olympics diver.
When two bodily functions happen at the exact same time. The excrement of fesses from the anus, while ejaculation of seamen comes out of the penis....creating a poogasim.