We found 21 dictionaries that define the word perpetual motion:

General (17 matching dictionaries)

1. perpetual motion: Longman Dictionary of Contemporary English
2. perpetual motion: Merriam-Webster
3. perpetual motion: Oxford Learner's Dictionaries
4. perpetual motion: American Heritage Dictionary of the English Language
5. perpetual motion: Collins English Dictionary
6. perpetual motion: Vocabulary.com
7. perpetual-motion, perpetual motion: Wordnik
8. perpetual motion: Wiktionary
9. perpetual motion: The Wordsmyth English Dictionary-Thesaurus
10. perpetual motion: Infoplease Dictionary
11. Perpetual motion, perpetual motion: Dictionary.com
12. Perpetual Motion (album), Perpetual Motion (film), Perpetual Motion (solitaire), Perpetual-motion, Perpetual motion (disambiguation), Perpetual motion: Wikipedia, the Free Encyclopedia
13. perpetual motion: Rhymezone
14. perpetual motion: FreeDictionary.org
15. perpetual motion: Mnemonic Dictionary
16. perpetual motion: TheFreeDictionary.com
17. Perpetual Motion: Dictionary of Phrase and Fable (1898)

Computing (1 matching dictionary)

18. Perpetual-motion, Perpetual motion: Encyclopedia

Miscellaneous (1 matching dictionary)

19. Brilliant Dream Dictionary (No longer online)

Slang (1 matching dictionary)

20. perpetual motion: Urban Dictionary

Tech (1 matching dictionary)

21. AUTOMOTIVE TERMS (No longer online)

(Note: See perpetual_motions as well.)

Definitions from Wiktionary (perpetual motion) ▸ noun:  (physics) The motion of some hypothetical device that continues forever with no external input of energy, in violation of the laws of thermodynamics. Similar: perpetual motion machine, permanent wave, conservation of energy, Brownian ratchet, permanence, translation, quantity of motion, thermodynamic equilibrium, zero-point energy, state of motion, more... Opposite: static, stationary, motionless, immobile, at rest Phrases: perpetual motion machine, perpetual motion machines, perpetual motion of the second kind, History of perpetual motion machines, more... ▸ Words similar to perpetual motion ▸ Usage examples for perpetual motion ▸ Idioms related to perpetual motion ▸ Wikipedia articles (New!) ▸ Words that often appear near perpetual motion ▸ Rhymes of perpetual motion ▸ Invented words related to perpetual motion