a sudden disaster or a violent event that causes change, for example a flood or a war （突然降临的）大灾难，大灾变，大动乱 to survive the cataclysm of the Black Death 幸免于黑死病的灾难
Word Originearly 17th cent. (originally denoting the biblical Flood described in Genesis): from French cataclysme, via Latin from Greek kataklusmos ‘deluge’, from kata- ‘down’ + kluzein ‘to wash’.