Source : Webster's Revised Unabridged Dictionary (1913)

   Note: Gas is often used adjectively or in combination; as,
         gas fitter or gasfitter; gas meter or gas-meter, etc.

   {Air gas} (Chem.), a kind of gas made by forcing air through
      some volatile hydrocarbon, as the lighter petroleums. The
      air is so saturated with combustible vapor as to be a
      convenient illuminating and heating agent.

   {Gas battery} (Elec.), a form of voltaic battery, in which
      gases, especially hydrogen and oxygen, are the active
      agents.

   {Gas carbon}, {Gas coke}, etc. See under {Carbon}, {Coke},
      etc.

   {Gas coal}, a bituminous or hydrogenous coal yielding a high
      percentage of volatile matters, and therefore available
      for the manufacture of illuminating gas. --R. W. Raymond.

   {Gas engine}, an engine in which the motion of the piston is
      produced by the combustion or sudden production or
      expansion of gas; -- especially, an engine in which an
      explosive mixture of gas and air is forced into the
      working cylinder and ignited there by a gas flame or an
      electric spark.