Wiktionary
perpetual motion machines
n. (perpetual motion machine English)
Usage examples of "perpetual motion machines".
The same one they use to reject applications for perpetual motion machines and reactionless drives - fails the standard for usefulness on the grounds of operativeness.
A few -for example, perpetual motion machines - can be excluded on grounds of fundamental physics.
It was like end-of-the-world stories, or perpetual motion machines.
But Fourmyle was in the library bludgeoning his librarian over the head with Bloch's Das Sexual Leben (eight pounds, nine ounces) because that unhappy man could produce no text on the manufacture of perpetual motion machines.