moat/ditch/fosse
A deep trench (in Europe usually filled with water) that surrounded a castle
1) A ditch, water filled or dry, around an enclosure
2) A water-filled ditch around a castle. A good example can be found at Bodiam Castle in East Sussex
3) The ditch surrounding a castle, filled with water when the castle was on a stream or river, but most often just a dry ditch. When wet, they did not contain alligators, but there was other revolting stuff in them
4) a deep trench usually filled with water that surrounded a castle
 Other texts that include ...