\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.

\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.]