abysm, abyss, arroyo, box canyon, breach, break, cavity, chap, chasm, check, chimney, chink, cleft, cleuch, clough, col, coulee, couloir, crack, cranny, crevasse, crevice, cut, cwm, defile, dell, dike, ditch, donga, draw, excavation, fault, fissure, flaw, flume, fracture, furrow, gap, gape, gash, gill, 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