Source : Webster's Revised Unabridged Dictionary (1913)

Joule's cycle \Joule's cycle\ (Thermodynamics)
   The cycle for the air engine proposed by Joule. In it air is
   taken by a pump from a cold chamber and compressed
   adiabatically until its pressure is eqal to that of the air
   in a hot chamber, into which it is then delivered, thereby
   displacing an equal amount of hot air into the engine
   cylinder. Here it expands adiabatically to the temperature of
   the cold chamber into which it is finally exhausted. This
   cycle, reversed, is used in refrigerating machines.