Moat

n. [O. Fr. mote, hill, dike, bank; N. Fr. motte, clod, turf; Sp. & Pg. mota, bank or mound of earth; It. motta, clod, mota, mud, dirt, turf; L. Lat. mota, motta, a hill on which a fort is built, an eminence, a dike; Prov. Ger. mott, bog-earth heaped up. The sense of bank or mound was transferred to the ditch adjoining, as dike signifies a ditch and a bank or mound of earth.] (Fort.) A deep trench round the rampart of a castle or other fortified place, sometimes filled with water; a ditch.