We found 13 dictionaries that define the word perpetual motion machine:

General (9 matching dictionaries)

1. perpetual motion machine: Merriam-Webster
2. perpetual motion machine: Vocabulary.com
3. perpetual motion machine: Wiktionary
4. perpetual-motion machine, perpetual motion machine: Dictionary.com
5. Perpetual-motion machine, Perpetual motion machine: Wikipedia, the Free Encyclopedia
6. perpetual motion machine: Rhymezone
7. perpetual motion machine: FreeDictionary.org
8. perpetual motion machine: Mnemonic Dictionary
9. perpetual motion machine: TheFreeDictionary.com

Computing (1 matching dictionary)

10. perpetual-motion machine, perpetual motion machine: Encyclopedia

Miscellaneous (1 matching dictionary)

11. perpetual motion machine: The Skeptic's Dictionary

Science (1 matching dictionary)

12. Perpetual Motion Machine: Eric Weisstein's World of Physics

Tech (1 matching dictionary)

13. AUTOMOTIVE TERMS (No longer online)

(Note: See perpetual_motion_machines as well.)

Definitions from Wiktionary (perpetual motion machine) ▸ noun:  (physics, pseudoscience) A hypothetical, pseudoscientific device that exhibits perpetual motion, especially one that does useful work with no input of energy. Similar: perpetual motion, Brownian ratchet, simple pendulum, quantity of motion, permanent magnet, aetherometry, pseudomomentum, pseudogravity, momentum, permanent wave, more... Opposite: entropy, friction, drag, deceleration, stoppage Types: overunity machine, over-unity machine, perpetuum mobile, more... ▸ Words similar to perpetual motion machine ▸ Usage examples for perpetual motion machine ▸ Idioms related to perpetual motion machine ▸ Wikipedia articles (New!) ▸ Words that often appear near perpetual motion machine ▸ Rhymes of perpetual motion machine ▸ Invented words related to perpetual motion machine