Meaning of perpetual motion

perpet'ual mo'tion

Pronunciation: [key]
— Mech. Mech.
  1. the motion of a theoretical mechanism that, without any losses due to friction or other forms of dissipation of energy, would continue to operate indefinitely at the same rate without any external energy being applied to it.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.