The Collaborative International Dictionary of English v.0.48:
Cataclysmal \Cat`a*clys"mal\, Cataclysmic \Cat`a*clys"mic\, a. Of or pertaining to a cataclysm. [1913 Webster]WordNet (r) 3.0 (2006):
cataclysmal adj 1: severely destructive; "cataclysmic nuclear war"; "a cataclysmic earthquake" [syn: cataclysmal, cataclysmic]