The Collaborative International Dictionary of English v.0.48:

Gear \Gear\, v. i. (Mach.)
   To be in, or come into, gear.
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The Collaborative International Dictionary of English v.0.48:

Gear \Gear\ (g[=e]r), n. [OE. gere, ger, AS. gearwe clothing,
   adornment, armor, fr. gearo, gearu, ready, yare; akin to OHG.
   garaw[imac], garw[imac] ornament, dress. See Yare, and cf.
   Garb dress.]
   1. Clothing; garments; ornaments.
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            Array thyself in thy most gorgeous gear. --Spenser.
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   2. Goods; property; household stuff. --Chaucer.
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            Homely gear and common ware.          --Robynson
                                                  (More's
                                                  Utopia).
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   3. Whatever is prepared for use or wear; manufactured stuff
      or material.
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            Clad in a vesture of unknown gear.    --Spenser.
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   4. The harness of horses or cattle; trapping.
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   5. Warlike accouterments. [Scot.] --Jamieson.
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   6. Manner; custom; behavior. [Obs.] --Chaucer.
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   7. Business matters; affairs; concern. [Obs.]
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            Thus go they both together to their gear. --Spenser.
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   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.
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   9. pl. (Naut.) See 1st Jeer
      (b) .
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   10. Anything worthless; stuff; nonsense; rubbish. [Obs. or
       Prov. Eng.] --Wright.
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             That servant of his that confessed and uttered this
             gear was an honest man.              --Latimer.
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   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 gear or To throw out of gear (Mach.), to
      connect or disconnect (wheelwork or couplings, etc.); to
      put in, or out of, working relation.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Gear \Gear\ (g[=e]r) v. t. [imp. & p. p. Geared (g[=e]rd); p.
   pr. & vb. n. Gearing.]
   1. To dress; to put gear on; to harness.
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   2. (Mach.) To provide with gearing.
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   3. To adapt toward some specific purpose; as, they geared
      their advertising for maximum effect among teenagers.
      [PJC]

   Double geared, driven through twofold compound gearing, to
      increase the force or speed; -- said of a machine.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gear
    n 1: a toothed wheel that engages another toothed mechanism in
         order to change the speed or direction of transmitted
         motion [syn: gear, gear wheel, geared wheel,
         cogwheel]
    2: wheelwork consisting of a connected set of rotating gears by
       which force is transmitted or motion or torque is changed;
       "the fool got his tie caught in the geartrain" [syn:
       gearing, gear, geartrain, power train, train]
    3: a mechanism for transmitting motion for some specific purpose
       (as the steering gear of a vehicle) [syn: gear, gear
       mechanism]
    4: equipment consisting of miscellaneous articles needed for a
       particular operation or sport etc. [syn: gear,
       paraphernalia, appurtenance]
    v 1: set the level or character of; "She pitched her speech to
         the teenagers in the audience" [syn: gear, pitch]

Moby Thesaurus II by Grady Ward, 1.0:

166 Moby Thesaurus words for "gear":
   Hydromatic, accessories, accommodate, accouter, accouterments,
   action, adapt, adjust, apparatus, apparel, appendages, appliances,
   appoint, appointments, appurtenances, arm, armament, array, attire,
   automatic transmission, bag and baggage, baggage, bedizenment,
   belongings, chattels, clobber, clockworks, clothes, clothing, cog,
   cogwheel, conveniences, cordage, cording, costume, differential,
   differential gear, drapery, dress, dressing, drive train, duds,
   duffel, dunnage, effects, equip, equipage, equipment, facilities,
   facility, fashion, fatigues, feathers, fig, fit, fit out, fit up,
   fittings, fixtures, freewheel, furnish, furnishings, furniture,
   garb, garments, gear train, gearbox, gearing, gearshift, gearwheel,
   goods, guise, habiliment, habiliments, habit, heel, high,
   impedimenta, implements, innards, installations, intermediate,
   investiture, investment, junk, kit, linen, livery, low, luggage,
   machinery, man, materials, materiel, means, mechanism, motion,
   movement, movements, munition, munitions, neutral, outfit,
   overdrive, panoply, paraphernalia, plant, plumbing, possessions,
   power train, prepare, rack, rags, raiment, regalia, reverse, rig,
   rig out, rig up, rigging, robes, ropework, roping, running rigging,
   service, serving, servomechanism, shit, sportswear, staff,
   standard transmission, standing rigging, stick shift,
   stock-in-trade, stuff, style, suit, supplies, synchromesh, tack,
   tackle, tackling, tailor, things, threads, togs, toilette, tools,
   transmission, trappings, traps, trim, turn out, uniform, utensils,
   vestment, vestments, vesture, watchworks, wear, wearing apparel,
   wheels, wheels within wheels, whipping, workings, works