What is a "seiche"?

I wrote about the phenomenon of a "seiche" in my first book, 

A 1,000-MILE WALK ON THE BEACH.

Earlier this month, weather conditions were perfect to set up large seiche formation on both Lakes Superior and Michigan.
(For a report on the Lake Superior seiche, go HERE.)

So, what is a "seiche" (pronounced SAY-sh)?

From the NOAA website:

Seiches are typically caused when strong winds and rapid changes in atmospheric pressure push water from one end of a body of water to the other. When the wind stops, the water rebounds to the other side of the enclosed area. The water then continues to oscillate back and forth for hours or even days. 

In 1954, a large seiche formed in Lake Michigan that bounced off the eastern shoreline of SW Michigan, then rebounded back across the lake as a 10-foot wave that swept fishermen off the docks of Chicago. Eight people drown that day.

For more information on this phenomenon and photos, go here.