perpetual-motion machine
A machine that could run forever. A perpetual-motion machine would have to produce at least as much energy as was needed for its operation. According to the second law of thermodynamics, such a machine is impossible, and to date none has ever been successfully demonstrated.
Words nearby perpetual-motion machine
perpetual calendar,
perpetual check,
perpetual debenture,
perpetual inventory,
perpetual motion,
perpetual-motion machine,
perpetuate,
perpetuity,
perphenazine,
perpignan,
perplex