Source : Webster's Revised Unabridged Dictionary (1913)

Gear \Gear\, n. [OE. gere, ger, AS. gearwe clothing, adornment,
   armor, fr. gearo, gearu, ready, yare; akin to OHG. garaw[=i],
   garw[=i] ornament, dress. See {Yare}, and cf. {Garb} dress.]
   1. Clothing; garments; ornaments.

            Array thyself in thy most gorgeous gear. --Spenser.

   2. Goods; property; household stuff. --Chaucer.

            Homely gear and common ware.          --Robynson
                                                  (More's
                                                  Utopia).

   3. Whatever is prepared for use or wear; manufactured stuff
      or material.

            Clad in a vesture of unknown gear.    --Spenser.

   4. The harness of horses or cattle; trapping.

   5. Warlike accouterments. [Scot.] --Jamieson.

   6. Manner; custom; behavior. [Obs.] --Chaucer.

   7. Business matters; affairs; concern. [Obs.]

            Thus go they both together to their gear. --Spenser.

   8. (Mech.)
      (a) A toothed wheel, or cogwheel; as, a spur gear, or a
          bevel gear; also, toothed wheels, collectively.
      (b) An apparatus for performing a special function;
          gearing; as, the feed gear of a lathe.
      (c) Engagement of parts with each other; as, in gear; out
          of gear.

   9. pl. (Naut.) See 1st {Jeer}
      (b) .

   10. Anything worthless; stuff; nonsense; rubbish. [Obs. or
       Prov. Eng.] --Wright.

             That servant of his that confessed and uttered this
             gear was an honest man.              --Latimer.

   {Bever gear}. See {Bevel gear}.

   {Core gear}, a mortise gear, or its skeleton. See {Mortise
      wheel}, under {Mortise}.

   {Expansion gear} (Steam Engine), the arrangement of parts for
      cutting off steam at a certain part of the stroke, so as
      to leave it to act upon the piston expansively; the
      cut-off. See under {Expansion}.

   {Feed gear}. See {Feed motion}, under {Feed}, n.

   {Gear cutter}, a machine or tool for forming the teeth of
      gear wheels by cutting.

   {Gear wheel}, any cogwheel.

   {Running gear}. See under {Running}.

   {To throw} {in, or out of}, {gear} (Mach.), to connect or
      disconnect (wheelwork or couplings, etc.); to put in, or
      out of, working relation.

Source : WordNet®

gear wheel
     n : a toothed wheel that engages another toothed mechanism in
         order to change the speed or direction of transmitted
         motion [syn: {gear}, {cogwheel}]