Sentence:  An extreme version of vorticity is a "vortex". The vortex is a spinning, cyclonic mass of fluid, which can be observed in the rotation of water going down a drain, as well as in smoke rings, tornados and <WSD>hurricanes</WSD>. 
Meaning of the word marked with <WSD> tags:  A severe tropical cyclone in the North Atlantic Ocean, Caribbean Sea, Gulf of Mexico, or in the eastern North Pacific off the west coast of Mexico, with winds of 119 km/h (74 miles per hour) or greater accompanied by rain, lightning, and thunder that sometimes moves into temperate latitudes.