The idea of perpetual motion is the idea of something continuing to move for ever without getting energy from anything else.
perpetual motion in British English
noun
1. Also called: perpetual motion of the first kind
motion of a hypothetical mechanism that continues indefinitely without any external source of energy. It is impossible in practice because of friction
2. Also called: perpetual motion of the second kind
motion of a hypothetical mechanism that derives its energy from a source at a lower temperature. It is impossible in practice because of the second law of thermodynamics
perpetual motion in American English
the motion of a hypothetical device which, once set in motion, would operate indefinitely by creating its own energy in excess of that dissipated
Examples of 'perpetual motion' in a sentence
perpetual motion
His perpetual motion, boundless energy and sharp intelligence sum up the extra zip to their game.