a deep, wide ditch surrounding a castle, fort, or town, typically filled with water and intended as a defence against attack
护城河, 城壕; 壕沟, 壕堑。
with obj.［often as adj. moated］
surround (a place) with a moat
筑城壕（或壕沟）围绕：
词源
late Middle English: from Old French mote 'mound'.