Perpetual motion

(Mech.), an incessant motion conceived to be attainable by a machine supplying its own motive forces independently of any action from without, or which has within itself the means, when once set in motion, of continuing its motion perpetually, or until worn out, without any new application of external force;—also, the machine itself by means of which it is attempted, or supposed possible, to produce such motion:—an invention much sought after, but physically impossible.—Resultant motion. See RESULTANT.