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·clysmic (-klĭzmĭk), cat′a·clysmal (-klĭzməl) adj.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.