cyclone

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun 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.
• noun A violent tropical storm, especially one originating in the southwestern Pacific Ocean or Indian Ocean.
• noun A violent rotating windstorm, especially a tornado.
• noun Any of various devices using centrifugal force to separate materials.

from The Century Dictionary.

• noun The term introduced into meteorology by Piddington, in 1840, as a general name for the class of extensive storms at sea that were at that time supposed to be characterized by the revolution of air in circles about a calm center.
• noun Any atmospheric movement, gentle or rapid, general or local, on land or at sea, in which the wind blows spirally around and in toward a center.
• noun Popularly, a tornado (such as occur in the Western States), or any destructive storm. See tornado, waterspout, and whirlwind.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Meteor.) A violent storm, often of vast extent, characterized by high winds rotating about a calm center of low atmospheric pressure. This center moves onward, often with a velocity of twenty or thirty miles an hour.
• noun (Meteor.) In general, a condition of the atmosphere characterized by a central area of pressure much lower than that of surrounding areas, and a system of winds blowing inward and around (clockwise in the southern hemisphere and counter-clockwise in the northern); -- called also a low-area storm. It is attended by high temperature, moist air, abundant precipitation, and clouded sky. The term includes the hurricane, typhoon, and tropical storms; it should not be applied to the moderate disturbances attending ordinary areas of low pressure nor to tornadoes, waterspouts, or “twisters,” in which the vertical motion is more important than the horizontal.
• noun Middle U. S. A tornado. See above, and Tornado.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A system of winds rotating around a center of low atmospheric pressure.
• noun A low pressure system.
• noun The more or less violent, small-scale circulations such as tornadoes, waterspouts, and dust devils.
• noun A strong wind.
• noun A Southeastern and Indian Ocean weather phenomenon that results in wind speeds of around 150 to 200 km/h.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (meteorology) rapid inward circulation of air masses about a low pressure center; circling counterclockwise in the northern hemisphere and clockwise in the southern
• noun a violent rotating windstorm