A cyclone is any large system of winds that rotates about a centre of low atmospheric pressure in a clockwise direction north of the Equator and in a counterclockwise direction to the south. Cyclonic winds move across nearly all regions of the Earth except the equatorial belt and are generally associated with rain or snow. Also occurring in much the same areas are anticyclones, wind systems that rotate about a high-pressure centre. Anticyclones are so called because they have a flow opposite to that of cyclones--i.e., an outward-spiralling motion, with the winds rotating counterclockwise in the Northern Hemisphere and clockwise in the Southern.

Excerpt from the Encyclopedia Britannica without permission.