*cyclone*

n. [ Gr.&unr_;&unr_;&unr_;&unr_;&unr_; moving in a circle, p. pr. of &unr_;&unr_;&unr_;&unr_;&unr_;, fr. ky`klos circle. ] 1. (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. [ 1913 Webster ]

☞ The atmospheric disturbance usually accompanying a cyclone, marked by an onward moving area of high pressure, is called an anticyclone. [ 1913 Webster ]

2. (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. [ Webster 1913 Suppl. ]

3. A tornado. See above, and Tornado. [ Middle U. S. ] [ Webster 1913 Suppl. ]