1 a a violent, esp. social or political, upheaval or disaster. b a great change.
2 a great flood or deluge.
Derivatives:
cataclysmal adj. cataclysmic adj. cataclysmically adv.
Etymology: F cataclysme f. L cataclysmus f. Gk kataklusmos f. klusmos flood f. kluzo wash
Useful english dictionary. 2012.