What does "pneumatic" mean?

Additional senses

1. 2.Moved or worked by pressure or flow of air; as, a pneumatic instrument; a pneumatic engine.
2. 3.(Biol.) Fitted to contain air; Having cavities filled with air; as, pneumatic cells; pneumatic bones. 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.