The Collaborative International Dictionary of English v.0.48:

Crevasse \Cre`vasse"\ (kr?`v?s"), n. [F. See Crevice.]
   1. A deep crevice or fissure, as in embankment; one of the
      clefts or fissure by which the mass of a glacier is
      divided.
      [1913 Webster]

   2. A breach in the levee or embankment of a river, caused by
      the pressure of the water, as on the lower Mississippi.
      [U.S.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

crevasse
    n 1: a deep fissure

Moby Thesaurus II by Grady Ward, 1.0:

76 Moby Thesaurus words for "crevasse":
   abysm, abyss, arroyo, box canyon, breach, break, chap, chasm,
   check, chimney, chink, cleft, cleuch, clough, col, coulee, couloir,
   crack, cranny, crater, crevice, cut, cwm, deep, defile, dell,
   depth, dike, ditch, donga, draw, excavation, fault, fissure, flaw,
   flume, fracture, furrow, gap, gape, gash, gorge, groove, gulch,
   gulf, gully, hole, hollow, incision, joint, kloof, leak, moat,
   notch, nullah, opening, pass, passage, pit, ravine, rent, rift,
   rime, rupture, scissure, seam, shaft, slit, slot, split, trench,
   valley, void, wadi, well, yawning abyss