Steam engine

Back-acting 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 pumps, etc.

Semiportable steam engine — a steam engine combined with, and attached to, a steam boiler, but not mounted on wheels.