|an engine that uses the thermal energy of steam to produce mechanical work, esp one in which steam from a boiler is expanded in a cylinder to drive a reciprocating piston|
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An engine in which the energy of hot steam is converted into mechanical power, especially an engine in which the force of expanding steam is used to drive one or more pistons. The source of the steam is typically external to the part of the machine that converts the steam energy into mechanical energy. Compare internal-combustion engine.