a storm or system of winds that rotates about a centre of low atmospheric pressure, advances at high speeds, and often brings abundant rain
a tornado
a region of low atmospheric pressure; = low2 (2)
cyclonic /sieʹklonik/ adj
cyclonically /sieʹklonikli/ adv
[Greek kyklōma wheel, coil, from kykloun to go round, from kyklos circle]