The Collaborative International Dictionary of English v.0.48:

Catastrophic \Cat`a*stroph"ic\, a.
   Of a pertaining to a catastrophe. --B. Powell.
   [1913 Webster]

WordNet (r) 3.0 (2006):

catastrophic
    adj 1: extremely harmful; bringing physical or financial ruin;
           "a catastrophic depression"; "catastrophic illness"; "a
           ruinous course of action" [syn: catastrophic,
           ruinous]

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "catastrophic":
   baneful, black, calamitous, cataclysmal, cataclysmic, consuming,
   consumptive, deadly, demolishing, demolitionary, depredatory,
   desolating, destroying, destructive, devastating, dire, disastrous,
   doomful, fatal, fateful, fratricidal, grievous, insurrectionary,
   internecine, nihilist, nihilistic, radical, ravaging, revolutional,
   revolutionary, revulsionary, revulsive, ruining, ruinous,
   self-destructive, subversionary, subversive, suicidal, sweeping,
   tragic, transilient, vandalic, vandalish, vandalistic, wasteful,
   wasting, withering, wreckful