The Collaborative International Dictionary of English v.0.48:

Rifle \Ri"fle\, n. [Akin to Dan. rifle, or riffel, the rifle of
   a gun, a chamfer (cf. riffel, riffelb["o]sse, a rifle gun,
   rifle to rifle a gun, G. riefeln, riefen, to chamfer,
   groove), and E. rive. See Rive, and cf. Riffle, Rivel.]
   1. A gun, the inside of whose barrel is grooved with spiral
      channels, thus giving the ball a rotary motion and
      insuring greater accuracy of fire. As a military firearm
      it has superseded the musket.
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   2. pl. (Mil.) A body of soldiers armed with rifles.
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   3. A strip of wood covered with emery or a similar material,
      used for sharpening scythes.
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   Rifle pit (Mil.), a trench for sheltering sharpshooters.
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