Source : Webster's Revised Unabridged Dictionary (1913)

Sidewinder \Side"wind`er\, n.
   1. (Zo["o]l.) See Horned rattler, under {Horned}.

   2. A heavy swinging blow from the side, which disables an
      adversary. [Slang.]

Source : WordNet®

sidewinder
     n 1: small pale-colored desert rattlesnake of southwestern United
          States; body moves in an s-shaped curve [syn: {horned
          rattlesnake}, {Crotalus cerastes}]
     2: air-to-air missile with infrared homing device