A violent whirling wind; specifically (Meteorol.), a tempest distinguished by a rapid whirling and slow progressive motion, usually accompaned with severe thunder, lightning, and torrents of rain, and commonly of short duration and small breadth; a small cyclone<-- twister -->.
A violent whirl, generally cyclonic in sense, averaging about 100 miles in diameter and with an intense vertical current at the centre. Associated winds may attain speeds of about 200 knots. Heavy rain, and generally thunder and lightning, occur with the tornado. The term 'tornado' has also been used for thunderstorm squalls in West Africa.
The most violent vortex storm on earth. Most commonly, tornados originate within a thunderstorm, although other processes can produce weaker tornados. Tornado strength can be classified on the Fujita scale of intensity which numbers from 0 to 5. F5 tornados are the most destructive known, with winds over 250 possible. F0 tornados are the weakest, though they can still produce significant damage.