THESAURUS
dell
abysm, abyss, arroyo, bottom, bottom glade, bottoms, box canyon, breach, break, canyon, cavity, chap, chasm, check, chimney, chink, cleft, cleuch, clough, col, coulee, couloir, crack, cranny, crevasse, crevice, cut, cwm, dale, defile, dike, dingle, ditch, donga, draw, excavation, fault, fissure, flaw, flume, fracture, furrow, gap, gape, gash, gill, glen, gorge, groove, grove, gulch, gulf, gully, hole, 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, valley, void, wadi
ROGET THESAURUS
dell
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.