Pile \Pile\, n. [AS. p[imac]l arrow, stake, L. pilum javelin;
   but cf. also L. pila pillar.]
   1. A large stake, or piece of timber, pointed and driven into
      the earth, as at the bottom of a river, or in a harbor
      where the ground is soft, for the support of a building, a
      pier, or other superstructure, or to form a cofferdam,
      etc.
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   Note: Tubular iron piles are now much used.
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   2. [Cf. F. pile.] (Her.) One of the ordinaries or
      subordinaries having the form of a wedge, usually placed
      palewise, with the broadest end uppermost.
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   Pile bridge, a bridge of which the roadway is supported on
      piles.

   Pile cap, a beam resting upon and connecting the heads of
      piles.

   Pile driver, or Pile engine, an apparatus for driving
      down piles, consisting usually of a high frame, with
      suitable appliances for raising to a height (by animal or
      steam power, the explosion of gunpowder, etc.) a heavy
      mass of iron, which falls upon the pile.

   Pile dwelling. See Lake dwelling, under Lake.

   Pile plank (Hydraul. Eng.), a thick plank used as a pile in
      sheet piling. See Sheet piling, under Piling.

   Pneumatic pile. See under Pneumatic.

   Screw pile, one with a screw at the lower end, and sunk by
      rotation aided by pressure.
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Pneumatic \Pneu*mat"ic\, Pneumatical \Pneu*mat"ic*al\, a. [L.
   pneumaticus, Gr. ?, fr. ?, ?, wind, air, ? to blow, breathe;
   cf. OHG. fnehan: cf. F. pneumatique. Cf. Pneumonia.]
   1. Consisting of, or resembling, air; having the properties
      of an elastic fluid; gaseous; opposed to dense or solid.
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            The pneumatical substance being, in some bodies, the
            native spirit of the body.            --Bacon.
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   2. Of or pertaining to air, or to elastic fluids or their
      properties; pertaining to pneumatics; as, pneumatic
      experiments. "Pneumatical discoveries." --Stewart.
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   3. Moved or worked by pressure or flow of air; as, a
      pneumatic instrument; a pneumatic engine.
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   4. (Biol.) Fitted to contain air; Having cavities filled with
      air; as, pneumatic cells; pneumatic bones.
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   5. Adapted for containing compressed air; inflated with air;
      as, a pneumatic cushion; a pneumatic tire, a tire formed
      of an annular tube of flexible fabric, as India rubber,
      suitable for being inflated with air.
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   Pneumatic action, or Pneumatic lever (Mus.), a
      contrivance for overcoming the resistance of the keys and
      other movable parts in an organ, by causing compressed air
      from the wind chest to move them.

   Pneumatic dispatch, a system of tubes, leading to various
      points, through which letters, packages, etc., are sent,
      by the flow and pressure of air.

   Pneumatic elevator, a hoisting machine worked by compressed
      air.

   Pneumatic pile, a tubular pile or cylinder of large
      diameter sunk by atmospheric pressure.

   Pneumatic pump, an air-exhausting or forcing pump.

   Pneumatic railway. See Atmospheric railway, under
      Atmospheric.

   Pneumatic syringe, a stout tube closed at one end, and
      provided with a piston, for showing that the heat produced
      by compressing a gas will ignite substances.

   Pneumatic trough, a trough, generally made of wood or sheet
      metal, having a perforated shelf, and used, when filled
      with water or mercury, for collecting gases in chemical
      operations.

   Pneumatic tube. See Pneumatic dispatch, above.
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