From Greek kataklusmos, the biblical term for the event Noah survived. (The Hebrew term is mabbuwl.)
a sudden violent change in the earth's surface
an event resulting in great loss and misfortune; "the whole city was affected by the irremediable calamity"; "the earthquake was a disaster"
an event or catastrophe in which great changes happen
a violent, large-scale natural disaster
n. Any overwhelming flood of water.
a sudden awful or violent event that shocks one
The cataclysm is the Greek expression for the Biblical Great Flood of Noah, from the Greek kataklysmos, to "wash down." Erudite Bible studies drew it into the English language in 1633.
In the Dragonlance books, the Cataclysm (Great Destruction) was a catastrophic event that occurred when the Kingpriest of Istar demanded to be given godlike powers in order to eliminate evil from the world.