Source : Webster's Revised Unabridged Dictionary (1913)

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.

   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.]

Source : WordNet®

crevasse
     n : a deep fissure