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).
When swimming pool water generates massive tsunami wave action from an earthquake as seen in videos taken at the time of the Baja / SoCal earthquake on 4/4/10.
I was on the phone during the earthquake and noticed my chandelier swaying, and when I looked out the window at the swimming pool, the water was making huge waves, which splashed up and out of the pool, the waves kept doing that for several minutes, it was like a Pool-Nami! But I didn't have my cell phone on to shoot a video clip for youtube.
The wave of shit that will end up all over the male crotchal area when pulling out too quickly after anal sex.
Little Jimmy finished the deed, and begin to pull out. Unfortunately he had forgotten what Barry had said about pulling out after Anal sex (pulling out way faster than he should have) and so his genitalia were obliterated by the ensuing poonami.