Source : Webster's Revised Unabridged Dictionary (1913)

Isodiabatic \I`so*di`a*bat"ic\, a. [Iso- + Gr. ? to pass
   through.] (Physics)
   Pertaining to the reception or the giving out of equal
   quantities of heat by a substance. --Rankine.

   {Isodiabatic lines} or {curves}, a pair of lines or curves
      exhibiting, on a diagram of energy, the law of variation
      of the pressure and density of a fluid, the one during the
      lowering, and the other during the raising, of its
      temperature, when the quantity of heat given out by the
      fluid during any given stage of the one process is equal
      to the quantity received during the corresponding stage of
      the other. Such lines are said to be isodiabatic with
      respect to each other. Compare {Adiabatic}.