steam engine

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An engine that converts the heat energy of pressurized steam into mechanical energy, especially one in which steam drives a piston in a closed cylinder.

from The Century Dictionary.

• noun An engine in which the mechanical force arising from the elasticity and expansive action of steam, or from its property of rapid condensation, or from the combination of the two, is made available as a motive power.
• noun A compound steam-engine.

from the GNU version of the Collaborative International Dictionary of English.

• An engine moved by steam.
• a steam engine in which the motion is transmitted backward from the crosshead to a crank which is between the crosshead and the cylinder, or beyond the cylinder.
• a steam engine combined with, and attached to, a boiler which is mounted on wheels so as to admit of easy transportation; -- used for driving machinery in the field, as thrashing machines, draining pumps, etc.
• a steam engine combined with, and attached to, a steam boiler, but not mounted on wheels.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A piston engine driven by steam (as contrasted, for example, with a steam turbine).
• noun Any heat engine that uses steam as its primary working fluid to do mechanical work.
• noun UK A steam locomotive.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun external-combustion engine in which heat is used to raise steam which either turns a turbine or forces a piston to move up and down in a cylinder