This is out of Webster handy college dictionary, third edition
engine: n. 1, any machine that converts energy into work. 2, any mechanical contrivance. 3, a railroad locomotive.
motor: n. 1, a source of mechanical power. 2, a machine that transforms the energy of water, steam, electricity, etc. into mechanical energy; engine. 3, an automobile: motor car. adj. 1, causing or imparting motion. 2, automobile.
contrivance: n. 1, a mechanical device. 2, a means of doing.