I have this WeatherBug thing running on my PC, and when there’s all sorts of nasty weather (like we’ve been having for the past week) it sends out warnings to your desktop.
Just now, I received this:

Lakeshore Flood Statement National Weather Service Chicago IL 1137 AM CDT Fri May 21 2004
There Will Be A Seiche Along The Southern And Southwest Shores Of Lake Michigan. The Water Level Will Rise To Around Two Feet Along The Shores Cook County Illinois And Lake County Illinois….

Whoa, a “seiche!” I sure as heck didn’t expect a “seiche.”
Okay, I have no idea what a seiche is. But this is what I learned from Merriam-Webster:

: an oscillation of the surface of a landlocked body of water (as a lake) that varies in period from a few minutes to several hours

So I guess it’s like Lake Michigan has turned into some sorta big ol’ bathtub and the water is sloshing around in it. Just like when you were taking a bath as a kid and you did that sliding-back-and-forth thing that your parents yelled at you about.