Source : Webster's Revised Unabridged Dictionary (1913)

   1. A contrivance attached to some elevated object for the
      purpose of showing which way the wind blows; a
      weathercock. It is usually a plate or strip of metal, or
      slip of wood, often cut into some fanciful form, and
      placed upon a perpendicular axis around which it moves
      freely.

            Aye undiscreet, and changing as a vane. --Chaucer.

   2. Any flat, extended surface attached to an axis and moved
      by the wind; as, the vane of a windmill; hence, a similar
      fixture of any form moved in or by water, air, or other
      fluid; as, the vane of a screw propeller, a fan blower, an
      anemometer, etc.

   3. (Zo["o]l.) The rhachis and web of a feather taken
      together.

   4. One of the sights of a compass, quadrant, etc.

   {Vane of a leveling staff}. (Surv.) Same as {Target}, 3.