a low-lying piece of land reclaimed from the sea or a river and protected by a dyke

a piece of reclaimed land, either from the sea or a lake

Area of low lying land protected from inundation by a perimeter bund or dyke.

A term used in Holland for an area reclaimed from the sea or lake. A dyke is constructed around the area which is then drained by pumping the water out. Polders form valuable agricultural land or pasture land for cattle.

A polder is a low-lying tract of land that forms an artificial hydrological entity, enclosed by embankments known as dikes. The best-known examples are those polders that constitute areas of land reclaimed from a body of water, such as a lake or the sea, and are consequently below the surrounding water level. This requires drainage by pumps to prevent the water table within the polder from rising too high.