a) A giant wave generated by an undersea earthquake, landslide or by a meteor impact.
b) Splashing of water in the toilet caused by plopping a big turd.

A tsunami is a bathroom prank that can be performed as follows:
1. Wait for one of your buddies to use a public bathroom stall.
2. Fill up a couple of buckets of water and gather outside the bathroom with other willing participants.
3. Walk into the bathroom and shut off the lights.
4. Get your helpers to start banging on the walls of the stall while yelling, "TSUNAMI," at the top of their lungs.
5. Dump the water on your soon to be ex-buddy.
6. Run away. It'll be a few minutes before he finishes up and starts looking for you.

In Ohio, it means you are about to get it in, in Japan, it means your shit just got fucked up.

A rippling motion starting from the boobs downwards towards the genitals, causing a semi erect penis to ripple too. this causing immense pleasure for the receiver, as well as an instinctual wave of extra cum when the fat guy finishes up.

When a day trade turns into a position trade

when an asian girl squirts pussy juice while reaching climax during intercourse

1. Massive waves sometimes up to a thousand feet high caused by undersea earthquakes or volcanic eruptions.

-From Japanese, port (tsu) wave (nami).

2. A large, unstopable force.

3. A character on the popular anime "Tenchi Muyo!"