noun

1. loosely a windstorm with a violent, whirling movement; tornado or hurricane
2. Meteorol. a system of rotating winds over a vast area, spinning inward to a low pressure center (counterclockwise in the N Hemisphere) and generally causing stormy weather: commonly called a low, since it coexists with low barometric pressure

Etymology: altered < cyclome (< Gr kyklōma, wheel), infl. by Gr kyklōn, moving in a circle < kykloein, to circle around, whirl < kyklos: see wheel