plāˈnāshən, pləˈ- noun
( -s )
Etymology: plane (IV) + -ation
: a process of erosion that produces flat surfaces: as
a. : lateral erosion by a meandering stream that widens its floodplain
b. : erosion by waves and currents that results in wave-cut platforms
c. : abrasive action of a glacier or of wind that planes or facets a previously rounded or irregular stone