A violent upheaval that causes great destruction or brings about a fundamental change.
A violent and sudden change in the earth's crust.
A devastating flood.
[French cataclysme, from Latin cataclysmos, deluge, from Greek kataklusmos, from katakluzein, to inundate : kata-, intensive pref.; see cata- + kluzein, to wash away.] cat'a·clys'mic (-klĭz'mĭk), cat'a·clys'mal (-klĭz'məl) adj., cat'a·clys'mi·cal·ly adv.