Cyclone \Cy"clone\, n.

1. (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.

2. A tornado. See above, and Tornado. [Middle U. S.]

Source: Webster's Revised Unabridged Dictionary (1913)
 

Cyclone \Cy"clone\ (s?"kl?n), n. [Gr.????? moving in a circle, p. pr. of ?????, fr. ky`klos circle.]

(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.

Note: The atmospheric disturbance usually accompanying a cyclone, marked by an onward moving area of high pressure, is called an anticyclone.

Source: Webster's Revised Unabridged Dictionary (1913)