1. (n.) That unwatered portion of a valley which forms its continuation beyond and above the most elevated spring that issues into it.

2. (n.) See Comb.

abysm abyss arroyo box canyon breach break canyon cavity chap chasm check chimney chink cirque cleft cleuch clough col combe corrie coulee couloir crack cranny crevasse crevice cut defile dell dike ditch donga draw excavation fault fissure flaw flume fracture furrow gap gape gash gorge groove gulch gulf gully hole incision joint kloof leak moat notch nullah opening pass passage ravine rent rift rime rupture scissure seam slit slot split trench valley void wadi