cat ‧ a ‧ clys ‧ m /ˈkætəklɪz ə m/ BrE AmE noun [countable]
[ Date: 1600-1700 ; Language: French ; Origin: cataclysme , from Latin , from Greek , from kataklyzein 'to flood' , from kata- 'down' + klyzein 'to wash' ]
literary a violent or sudden event or change, such as a serious flood or ↑ earthquake
—cataclysmic /ˌkætəˈklɪzmɪk◂/ adjective