[1] : The Collaborative International Dictionary of English v.0.48

cataclysm \cat"aclysm\, n. l. cataclysmos, gr. kataklysmo`s,
   from ? to dash over, inundate; kata` downward, against + ? to
   wash or dash over: cf. f. cataclysme.
   1. an extensive overflow or sweeping flood of water; a
      deluge.
      1913 webster

   2. geol. any violent catastrophe, involving sudden and
      extensive changes of the earth's surface.
      1913 webster cataclysmal

[2] : WordNet (r) 2.0

cataclysm
     n 1: a sudden violent change in the earth's surface syn: catastrophe
     2: an event resulting in great loss and misfortune; "the whole
        city was affected by the irremediable calamity"; "the
        earthquake was a disaster" syn: calamity, catastrophe,
         disaster, tragedy
see also:
catastrophe calamity disaster tragedy 

[3] : Moby Thesaurus II by Grady Ward, 1.0

91 moby thesaurus words for "cataclysm":
   accident, alluvion, alluvium, apoplexy, bloodless revolution, blow,
   bouleversement, breakdown, breaking up, breakup, calamity,
   casualty, cataract, catastrophe, cave, cave-in, clean slate,
   clean sweep, climax, collapse, collision, computer revolution,
   contretemps, convulsion, counterrevolution, crack-up, crash,
   debacle, deluge, diastrophism, disaster, engulfment, fit, flood,
   flooding, grief, ill hap, inundation, misadventure, mischance,
   misfortune, mishap, nasty blow, overflow, overflowing, overrunning,
   overthrow, overturn, palace revolution, paroxysm, pileup, pour,
   quake, radical change, revolt, revolution, revolutionary war,
   revulsion, shipwreck, shock, smash, smashup, spasm, spate, spill,
   spillage, staggering blow, striking alteration, stroke, submersion,
   subversion, sweeping change, tabula rasa, technological revolution,
   temblor, the deluge, the flood, tidal wave, torrent, total change,
   total loss, tragedy, transilience, tsunami, upheaval, upset,
   violent change, washout, whelming, wrack, wreck

Cataclysm >> C Words
Cataclysm, definition of term: Cataclysm
cataclysm_pag1.html