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1. A violent upheaval that causes great destruction or brings about a fundamental change.
2. A violent and sudden change in the earth's crust.
3. 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.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Adj.1.cataclysmal - severely destructive; "cataclysmic nuclear war"; "a cataclysmic earthquake"
destructive - causing destruction or much damage; "a policy that is destructive to the economy"; "destructive criticism"


References in classic literature ?
After this season of congealed dampness came a spell of dry frost, when strange birds from behind the North Pole began to arrive silently on the upland of Flintcomb-Ash; gaunt spectral creatures with tragical eyes--eyes which had witnessed scenes of cataclysmal horror in inaccessible polar regions of a magnitude such as no human being had ever conceived, in curdling temperatures that no man could endure; which had beheld the crash of icebergs and the slide of snow-hills by the shooting light of the Aurora; been half blinded by the whirl of colossal storms and terraqueous distortions; and retained the expression of feature that such scenes had engendered.
Scots will not accept a botched deal by Boris or a cataclysmal no-deal Brexit.
Nearly 45 years after this 1883 cataclysmal eruption, Anak Krakatau (aChild of Krakataua in Indonesian) emerged from the sea in the same location as the former Krakatau, and grew to reach about 338 meters (1,108 feet), its maximum height on December 22, 2018.