The Collaborative International Dictionary of English v.0.48:

Wheel \Wheel\ (hw[=e]l), n. [OE. wheel, hweol, AS. hwe['o]l,
   hweogul, hweowol; akin to D. wiel, Icel. hv[=e]l, Gr.
   ky`klos, Skr. cakra; cf. Icel. hj[=o]l, Dan. hiul, Sw. hjul.
   [root]218. Cf. Cycle, Cyclopedia.]
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   1. A circular frame turning about an axis; a rotating disk,
      whether solid, or a frame composed of an outer rim, spokes
      or radii, and a central hub or nave, in which is inserted
      the axle, -- used for supporting and conveying vehicles,
      in machinery, and for various purposes; as, the wheel of a
      wagon, of a locomotive, of a mill, of a watch, etc.
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            The gasping charioteer beneath the wheel
            Of his own car.                       --Dryden.
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   2. Any instrument having the form of, or chiefly consisting
      of, a wheel. Specifically:
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      (a) A spinning wheel. See under Spinning.
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      (b) An instrument of torture formerly used.
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                His examination is like that which is made by
                the rack and wheel.               --Addison.
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   Note: This mode of torture is said to have been first
         employed in Germany, in the fourteenth century. The
         criminal was laid on a cart wheel with his legs and
         arms extended, and his limbs in that posture were
         fractured with an iron bar. In France, where its use
         was restricted to the most atrocious crimes, the
         criminal was first laid on a frame of wood in the form
         of a St. Andrew's cross, with grooves cut transversely
         in it above and below the knees and elbows, and the
         executioner struck eight blows with an iron bar, so as
         to break the limbs in those places, sometimes finishing
         by two or three blows on the chest or stomach, which
         usually put an end to the life of the criminal, and
         were hence called coups-de-grace -- blows of mercy. The
         criminal was then unbound, and laid on a small wheel,
         with his face upward, and his arms and legs doubled
         under him, there to expire, if he had survived the
         previous treatment. --Brande.
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      (c) (Naut.) A circular frame having handles on the
          periphery, and an axle which is so connected with the
          tiller as to form a means of controlling the rudder
          for the purpose of steering.
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      (d) (Pottery) A potter's wheel. See under Potter.
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                Then I went down to the potter's house, and,
                behold, he wrought a work on the wheels. --Jer.
                                                  xviii. 3.
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                Turn, turn, my wheel! This earthen jar
                A touch can make, a touch can mar. --Longfellow.
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      (e) (Pyrotechny) A firework which, while burning, is
          caused to revolve on an axis by the reaction of the
          escaping gases.
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      (f) (Poetry) The burden or refrain of a song.
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   Note: "This meaning has a low degree of authority, but is
         supposed from the context in the few cases where the
         word is found." --Nares.
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               You must sing a-down a-down,
               An you call him a-down-a.
               O, how the wheel becomes it!       --Shak.
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   3. A bicycle or a tricycle; a velocipede.
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   4. A rolling or revolving body; anything of a circular form;
      a disk; an orb. --Milton.
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   5. A turn revolution; rotation; compass.
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            According to the common vicissitude and wheel of
            things, the proud and the insolent, after long
            trampling upon others, come at length to be trampled
            upon themselves.                      --South.
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            [He] throws his steep flight in many an aery wheel.
                                                  --Milton.
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   A wheel within a wheel, or Wheels within wheels, a
      complication of circumstances, motives, etc.

   Balance wheel. See in the Vocab.

   Bevel wheel, Brake wheel, Cam wheel, Fifth wheel,
   Overshot wheel, Spinning wheel, etc. See under Bevel,
      Brake, etc.

   Core wheel. (Mach.)
      (a) A mortise gear.
      (b) A wheel having a rim perforated to receive wooden
          cogs; the skeleton of a mortise gear.

   Measuring wheel, an odometer, or perambulator.

   Wheel and axle (Mech.), one of the elementary machines or
      mechanical powers, consisting of a wheel fixed to an axle,
      and used for raising great weights, by applying the power
      to the circumference of the wheel, and attaching the
      weight, by a rope or chain, to that of the axle. Called
      also axis in peritrochio, and perpetual lever, -- the
      principle of equilibrium involved being the same as in the
      lever, while its action is continuous. See Mechanical
      powers, under Mechanical.

   Wheel animal, or Wheel animalcule (Zool.), any one of
      numerous species of rotifers having a ciliated disk at the
      anterior end.

   Wheel barometer. (Physics) See under Barometer.

   Wheel boat, a boat with wheels, to be used either on water
      or upon inclined planes or railways.

   Wheel bug (Zool.), a large North American hemipterous
      insect (Prionidus cristatus) which sucks the blood of
      other insects. So named from the curious shape of the
      prothorax.

   Wheel carriage, a carriage moving on wheels.

   Wheel chains, or Wheel ropes (Naut.), the chains or ropes
      connecting the wheel and rudder.

   Wheel cutter, a machine for shaping the cogs of gear
      wheels; a gear cutter.

   Wheel horse, one of the horses nearest to the wheels, as
      opposed to a leader, or forward horse; -- called also
      wheeler.

   Wheel lathe, a lathe for turning railway-car wheels.

   Wheel lock.
      (a) A letter lock. See under Letter.
      (b) A kind of gunlock in which sparks were struck from a
          flint, or piece of iron pyrites, by a revolving wheel.
      (c) A kind of brake a carriage.

   Wheel ore (Min.), a variety of bournonite so named from the
      shape of its twin crystals. See Bournonite.

   Wheel pit (Steam Engine), a pit in the ground, in which the
      lower part of the fly wheel runs.

   Wheel plow, or Wheel plough, a plow having one or two
      wheels attached, to render it more steady, and to regulate
      the depth of the furrow.

   Wheel press, a press by which railway-car wheels are forced
      on, or off, their axles.

   Wheel race, the place in which a water wheel is set.

   Wheel rope (Naut.), a tiller rope. See under Tiller.

   Wheel stitch (Needlework), a stitch resembling a spider's
      web, worked into the material, and not over an open space.
      --Caulfeild & S. (Dict. of Needlework).

   Wheel tree (Bot.), a tree (Aspidosperma excelsum) of
      Guiana, which has a trunk so curiously fluted that a
      transverse section resembles the hub and spokes of a
      coarsely made wheel. See Paddlewood.

   Wheel urchin (Zool.), any sea urchin of the genus Rotula
      having a round, flat shell.

   Wheel window (Arch.), a circular window having radiating
      mullions arranged like the spokes of a wheel. Cf. Rose
      window, under Rose.
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WordNet (r) 3.0 (2006):

wheel horse
    n 1: a draft horse harnessed behind others and nearest the
         wheels of a vehicle [syn: wheel horse, wheeler]