1. (n.) A deep trench around the rampart of a castle or other fortified place, sometimes filled with water\; a ditch.

2. (v. t.) To surround with a moat.

abri abysm abyss approach trench aqueduct arch dam arroyo backstop bamboo curtain bank bar barrage barrier bear-trap dam beaver dam boom box canyon breach break breakwater breastwork brick wall buffer bulkhead bulwark bunker canal canalization canyon cavity channel chap chasm check chimney chink cleft cleuch clough cofferdam col communication trench coulee couloir countermine coupure crack cranny crevasse crevice crimp cut cwm dam defense defile dell dike ditch donga double sap draw dugout earthwork embankment entrenchment excavation fault fence fire trench fissure flaw flume flying sap fortified tunnel fosse foxhole fracture furrow gallery gap gape gash gate goffer gorge gravity dam groin groove gulch gulf gully gutter ha-ha hole hydraulic-fill dam incision iron curtain jam jetty joint kennel kloof leak leaping weir levee logjam milldam mine mole mound notch nullah opening parallel parapet pass passage pleat portcullis rampart ravine rent rift rime roadblock rock-fill dam rupture sap scissure seam seawall shutter dam slit slit trench slot split stone wall sunk fence trench trough tunnel valley void wadi wall weir wicket dam work