Definition of "freeboard"

(nautical) The vertical distance between the waterline and the uppermost watertight deck of a vessel.  examples

The distance between a water level and the top of something that contains or restrains it (such as a dam).  examples

The distance between the top of sea ice and the water level.  examples

A type of skateboard which simulates the movement of a snowboard when used on a downhill coarse, allowing snowboarding techniques, which has an addition of two centerline casters that extend below the traditional skateboard wheels and bogies.  examples