A facing of wood, stone, or any other material, to sustain an embankment when it receives a slope steeper than the natural slope; also, a retaining wall.
Retaining wall of stone or timber of an earth bank or sides of a ditch. (Kenyon, John R. Medieval Fortifications, 211)
A facing of facines, wood, sandbags, gabions, sod, or masonry to protect a wall or bank of earth (Earthwork)(Rampart). Designed to protect the interior slopes of the parapets from erosion or other damage which could cause failure of the wall.