[ After N. L. S. Carnot, French physicist. ] (Thermodynamics) An ideal heat-engine cycle in which the working fluid goes through the following four successive operations: (1) Isothermal expansion to a desired point; (2) adiabatic expansion to a desired point; (3) isothermal compression to such a point that (4) adiabatic compression brings it back to its initial state. [ Webster 1913 Suppl. ]