Wikipedia
A pediplain (from the Latin pes, genitive case pedis, meaning "foot") is a concept in geology and geomorphology that describe an extensive plain formed by the coalescence of pediments. The processes through which pediplains forms is known as pediplanation. The concepts of pediplain and pediplanation were first developed by geologist Lester Charles King in his 1942 book South African Scenery. The concept gained notoriety as it was juxtaposed to peneplanation.
Pediplanation is linked to scarp retreat in the following way: as scarps retreat over geological time pediments migrate and extend over large areas. The result is that the surface is eroded chiefly backward and that downward erosion is limited. In contrast to common peneplain conceptualizations several pediplains might form simultaneously at different altitudes and do not necessarily grade to a base level. Pediplains are normally formed in areas of arid and semi-arid climate.