A random wave at the beach, most commonly on the U.S. Northern Pacific Coast, that comes to shore much farther and higher than any of the other recent waves. They aren't noticeable beforehand from shore and "sneak" up on people unexpectedly, many times causing people to be pushed over, or even swept out to sea.
The sneaker wave at Thor's Well, Cape Perpetua, Oregon, was deadly as it swept to sea the unsuspecting photographer who had chosen to ignore the signs warning of impending danger.
by memanelson February 3, 2017