a deep, wide excavation that is usually filled with water and that goes around the walls of a place (such as a castle) to protect it from being attacked
ha-has, stanks(British dialect), sunk fencesdikes, ditches, fosses, gutters, sheughs(chiefly Scottish), trenches, troughsacequias(Southwest), culverts, drains, draws, gullies(also gulleys), ravinesdrills, furrowskennels
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