1》 a machine with moving parts that converts power into motion.
2》 (also railway ~ ) a locomotive.
3》 historical a mechanical device or instrument, especially one used in warfare.
The word ~ entered Middle English in the sense 'ingenuity, cunning', coming via Old French engin from Latin ingenium 'talent, device' (the root also of ingenious ). From the original sense arose 'the product of ingenuity, a plot or snare', also 'tool, weapon'; the latter use came to apply specifically to a large mechanical weapon, from which, in the mid 17th century, arose the idea of a machine.