The Collaborative International Dictionary of English v.0.48:

Debacle \De*ba"cle\, n. [F. d['e]b[^a]cle, fr. d['e]b[^a]cler to
   unbar, break loose; pref. d['e]- (prob. = L. dis) + b[^a]cler
   to bolt, fr. L. baculum a stick.]
   1. (Geol.) A breaking or bursting forth; a violent rush or
      flood of waters which breaks down opposing barriers, and
      hurls forward and disperses blocks of stone and other
      d['e]bris.
      [1913 Webster]

   2. A sudden breaking up or breaking loose; a violent
      dispersion or disruption; impetuous rush; outburst.
      [Webster 1913 Suppl.]

   3. a complete and ludicrous failure; a rout, as of an army; a
      great disaster; a fiasco.
      [PJC]

WordNet (r) 3.0 (2006):

debacle
    n 1: a sudden and violent collapse [syn: debacle, fiasco]
    2: flooding caused by a tumultuous breakup of ice in a river
       during the spring or summer
    3: a sound defeat [syn: thrashing, walloping, debacle,
       drubbing, slaughter, trouncing, whipping]