Tornado \Tor*na"do\, n.; pl. {Tornadoes}. [From Sp. or Pg.
   tornar to turn, return, L. tornare to turn, hence, a whirling
   wind. The Sp. & Pg. tornada is a return. See {Turn}.]
   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.
   
[1913 Webster]