Source : Webster's Revised Unabridged Dictionary (1913)

Avalanche \Av"a*lanche`\ (?; 277), n. [F. avalanche, fr. avaler
   to descend, to let down, from aval down, downward; ? (L. ad)
   + val, L. vallis, valley. See {Valley}.]
   1. A large mass or body of snow and ice sliding swiftly down
      a mountain side, or falling down a precipice.

   2. A fall of earth, rocks, etc., similar to that of an
      avalanche of snow or ice.

   3. A sudden, great, or irresistible descent or influx of
      anything.

Source : WordNet®

avalanche
     n 1: a slide of large masses of snow and ice and mud down a
          mountain
     2: a sudden appearance of an overwhelming number of things;
        "the program brought an avalanche of mail"
     v : of snow masses in the mountains [syn: {roll down}]