The Collaborative International Dictionary of English v.0.48:
Steam engine \Steam" en"gine\ ([e^]n"j[i^]n).
An engine moved by steam.
Note: In its most common forms its essential parts are a
piston, a cylinder, and a valve gear. The piston works
in the cylinder, to which steam is admitted by the
action of the valve gear, and communicates motion to
the machinery to be actuated. Steam engines are thus
classified: 1. According to the way the steam is used
or applied, as condensing, noncondensing, compound,
double-acting, single-acting, triple-expansion, etc. 2.
According to the motion of the piston, as
reciprocating, rotary, etc. 3. According to the motion
imparted by the engine, as rotative and nonrotative. 4.
According to the arrangement of the engine, as
stationary, portable, and semiportable engines,
horizontal and vertical engines, beam engine,
oscillating engine, direct-acting and back-acting
engines, etc. 5. According to their uses, as portable,
marine, locomotive, pumping, blowing, winding, and
stationary engines, the latter term referring to
factory engines, etc., and not technically to pumping
or blowing engines. Locomotive and portable engines are
usually high-pressure, noncondensing, rotative, and
direct-acting. Marine engines are high or low pressure,
rotative, and generally condensing, double-acting, and
compound. Paddle engines are generally beam,
side-lever, oscillating, or direct-acting. Screw
engines are generally direct-acting, back-acting, or
oscillating. Stationary engines belong to various
classes, but are generally rotative. A horizontal or
inclined stationary steam engine is called a left-hand
or a right-hand engine when the crank shaft and driving
pulley are on the left-hand side, or the right-hand
side, respectively, of the engine, to a person looking
at them from the cylinder, and is said to run forward
or backward when the crank traverses the upward half,
or lower half, respectively, of its path, while the
piston rod makes its stroke outward from the cylinder.
A marine engine, or the engine of a locomotive, is said
to run forward when its motion is such as would propel
the vessel or the locomotive forward. Steam engines are
further classified as double-cylinder, disk,
semicylinder, trunk engines, etc. Machines, such as
cranes, hammers, etc., of which the steam engine forms
a part, are called steam cranes, steam hammers, etc.
See Illustration in Appendix.
Back-acting steam engine, or Back-action steam engine, 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.
Portable steam engine, 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
Semiportable steam engine, a steam engine combined with,
and attached to, a steam boiler, but not mounted on