Northern and North Midland U.S.
1. an awkward, usually unintentional dive in which the front of the body strikes the water horizontally, the abdomen or chest bearing the brunt of the impact.
2. a maneuver with a sled in which the sledder runs with the sled to gain momentum and jumps forward to land on top of the sled as it moves through the snow.
Also, belly flopper .
[ 1890-95 ]