abysm, abyss, alveolation, alveolus, antrum, aperture, armpit, arroyo, basin, booth, bowl, box, box canyon, breach, break, broaching, canyon, cell, cellule, chamber, chap, chasm, check, chimney, chink, clearing, cleft, cleuch, clough, col, compartment, concave, concavity, coulee, couloir, crack, cranny, crater, crevasse, crevice, crib, crypt, cup, cut, cwm, deep, defile, dell, depression, depth, dike, dip, disclosure, ditch, donga, draw, enclosed space, excavation, fault, fenestra, fissure, fistula, flaw, flume, fold, follicle, fontanel, foramen, fracture, funnel chest, furrow, gap, gape, gash, gat, gorge, groove, gulch, gulf, gully, hiatus, hold, hole, hollow, hollow shell, incision, inlet, interval, joint, kloof, lacuna, laying open, leak, manger, moat, notch, nullah, opening, opening up, orifice, outlet, pass, passage, passageway, pew, pit, pocket, pore, punch bowl, ravine, rent, rift, rime, rupture, scissure, scoop, seam, shaft, shell, sink, sinus, slit, slot, socket, space, split, stall, stoma, throwing open, trench, trough, uncorking, unstopping, vacuity, valley, vault, void, vug, wadi, well, yawn, yawning abyss