THESAURUS
abysm, abyss, arroyo, bottom, bottom glade, bottoms, box canyon, breach, break, canyon, cavity, chap, chasm, check, chimney, chink, cirque, cleft, cleuch, clough, col, comb, combe, corrie, coulee, couloir, crack, cranny, crevasse, crevice, cut, cwm, dale, defile, dell, dike, dingle, ditch, donga, draw, excavation, fault, fissure, flaw, flume, fracture, furrow, gap, gape, gash, gill, glen, gorge, groove, grove, gulch, gulf, gully, hole, hollow, incision, intervale, joint, kloof, leak, lunar rill, moat, notch, nullah, opening, pass, passage, ravine, rent, rift, rime, rupture, scissure, seam, slit, slot, split, strath, trench, trough, vale, void, wadi
ROGET THESAURUS
Concavity
N
concavity, depression, dip, hollow, hollowness, indentation, intaglio, cavity, dent, dint, dimple, follicle, pit, sinus, alveolus, lacuna, excavation, strip mine, trough, honeycomb, cup, basin, crater, punch bowl, cell, socket,
valley, vale, dale, dell, dingle, combe, bottom, slade, strath, glade, grove, glen, cave, cavern, cove, grot, grotto, alcove, cul-de- sac, gully, arch, bay, excavator, sapper, miner, honeycomb (sponge), depressed, alveolate, calathiform, cup-shaped, dishing, favaginous, faveolate, favose, scyphiform, scyphose, concave, hollow, stove in, retiring, retreating, cavernous, porous, infundibul, infundibular, infundibuliform, funnel shaped, bell shaped, campaniform, capsular, vaulted, arched.