(n.) A sunk fence; a fence, wall, or ditch, not visible till one is close upon it.

arroyo bed canal canalization channel conduit course creek bed crimp culvert cut dike ditch donga dry bed duct entrenchment flume fosse goffer gulch gully gullyhole gutter ha-ha headrace irrigation ditch kennel moat nullah pleat race river bed riverway runnel sluice spillbox spillway stream bed streamway sunk fence swash swash channel tailrace trench trough wadi water carrier water channel water furrow water gap water gate watercourse waterway waterworks