2. Anything used to effect a purpose; any device or contrivance; an agent. You see the ways the fisherman doth take to catch the fish; what engines doth he make? (Bunyan) Their promises, enticements, oaths, tokens, and all these engines of lust. (Shak)
4. (Science: machinery) a compound machine by which any physical power is applied to produce a given physical effect. Engine driver, one who manages an engine; specifically, the engineer of a locomotive. Engine lathe.
The term engine is more commonly applied to massive machines, or to those giving power, or which produce some difficult result. Engines, as motors, are distinguished according to the source of power, as steam engine, air engine, electromagnetic engine; or the purpose on account of which the power is applied, as fire engine, pumping engine, locomotive engine; or some peculiarity of construction or operation, as single-acting or double-acting engine, high-pressure or low-pressure engine, condensing engine, etc.