[cat.a.clysm] n [F cataclysme, fr. L cataclysmos, fr. Gk kataklysmos, fr. kataklyzein to inundate, fr. kata- + klyzein to wash--more at clyster] (1637) 1: flood, deluge
2: catastrophe 3a
3: a momentous and violent event marked by overwhelming upheaval and demolition; broadly: an event that brings great changes -- cat.a.clys.mal or cat.a.clys.mic adj -- cat.a.clys.mi.cal.ly adv