The Collaborative International Dictionary of English v.0.48:

Pneumatic \Pneu*mat"ic\, n.
   A vehicle, as a bicycle, the wheels of which are fitted with
   pneumatic tires. [archaic]
   [Webster 1913 Suppl.] Pneumatic

The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

            The pneumatical substance being, in some bodies, the
            native spirit of the body.            --Bacon.
      [1913 Webster]

   2. Of or pertaining to air, or to elastic fluids or their
      properties; pertaining to pneumatics; as, pneumatic
      experiments. "Pneumatical discoveries." --Stewart.
      [1913 Webster]

   3. Moved or worked by pressure or flow of air; as, a
      pneumatic instrument; a pneumatic engine.
      [1913 Webster]

   4. (Biol.) Fitted to contain air; Having cavities filled with
      air; as, pneumatic cells; pneumatic bones.
      [1913 Webster]

   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.
      [Webster 1913 Suppl.]

   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.
      [1913 Webster]

WordNet (r) 3.0 (2006):

pneumatic
    adj 1: of or relating to or using air (or a similar gas);
           "pneumatic drill"; "pneumatic tire"

Moby Thesaurus II by Grady Ward, 1.0:

109 Moby Thesaurus words for "pneumatic":
   Junoesque, aerial, aeriform, aerodynamic, aerographic, aerologic,
   aeromechanical, aerophysical, aerostatic, aerotechnical, aery,
   agreeable, airish, airlike, airy, alfresco, amply endowed,
   atmospheric, bagging, baggy, ballooning, becoming, bellying,
   billowing, billowy, bloated, bonny, bosomy, braw, breezy, built,
   built for comfort, bulbose, bulbous, bulging, bumped, bumpy,
   bunched, bunchy, buxom, callipygian, callipygous, comely,
   curvaceous, curvy, distended, ethereal, exposed, fair, fuming,
   fumy, gaseous, gasified, gasiform, gaslike, gassy, goddess-like,
   good-looking, goodly, hillocky, hummocky, light, likely,
   lovely to behold, mephitic, miasmal, miasmatic, miasmic, moutonnee,
   open-air, oxyacetylene, oxygenous, ozonic, personable, pleasing,
   pneumatological, potbellied, pouching, presentable, reeking, reeky,
   roomy, rounded, shapely, sightly, slender, smoking, smoky, stacked,
   statuesque, steaming, steamy, swelling, tropospheric, vaporing,
   vaporish, vaporlike, vaporous, vapory, verrucated, verrucose,
   warty, well-built, well-favored, well-formed, well-made,
   well-proportioned, well-shaped, well-stacked