perpetual motion

American  

noun

Mechanics.

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.

---

perpetual motion British  

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

---

Etymology

Origin of perpetual motion

First recorded in 1585–95

Example Sentences

While we continue to see great merit in letting more information flow into the market before making decisions, we also recognize that many investors are addicted to perpetual motion.

From Barron's • Mar. 25, 2026

Mario is thus an ideal avatar: Cheerful, active, in perpetual motion and vague enough to represent whatever a gamer wants him to be.

From The Wall Street Journal • Feb. 27, 2026

“If that occurred with cloud seeding, they’d have water all the time. You can’t create rain out of thin air per se and get 6 inches of water. That’s akin to perpetual motion technology.”

From Seattle Times • Apr. 17, 2024

In the spinaron effect, the cobalt atom remains in perpetual motion, maintaining its magnetic essence despite its interaction with the electrons.

From Science Daily • Oct. 26, 2023

Just like the North Star and all its whirling, starry brethren, a person’s idea of where “home” is remains in perpetual motion, one’s whole life long.

From "The Hidden Gallery" by Maryrose Wood