cy·clone /ˈsaɪˌklon/
 颶風,暴風
 Cy·clone n.
 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.
 Note: ☞ The atmospheric disturbance usually accompanying a cyclone, marked by an onward moving area of high pressure, is called an anticyclone.
 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.
 3.  A tornado. See above, and Tornado. [Middle U. S.]
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 cyclone
      n 1: (meteorology) rapid inward circulation of air masses about a
           low-pressure center; circling counterclockwise in the
           northern hemisphere and clockwise in the southern [ant:
           anticyclone]
      2: a violent rotating windstorm