a. An atmospheric system characterized by the rapid inward circulation of air masses about a low-pressure center, usually accompanied by stormy, often destructive weather. Cyclones circulate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
b. A violent tropical storm, especially one originating in the southwestern Pacific Ocean or Indian Ocean.
2. A violent rotating windstorm, especially a tornado.
3. Any of various devices using centrifugal force to separate materials.
[From Greek kuklōn, present participle of kukloun, to rotate, from kuklos, circle; see kwel-1 in the Appendix of Indo-European roots.]
cy·clonic (-klŏnĭk), cy·cloni·cal adj.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 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.