from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The hypothetical continuous operation of an isolated mechanical device or other closed system without a sustaining energy source.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The motion of some hypothetical device that continues forever with no obvious input of energy in violation of the laws of thermodynamics.
from the GNU version of the Collaborative International Dictionary of English
- adj. See under Motion.
- n. an incessant motion conceived to be attainable by a machine supplying its own motive forces independently of any action from without. According to the law of conservation of energy, such perpetual motion is impossible, and no device has yet been built that is capable of perpetual motion.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. motion that continues indefinitely without any external source of energy; impossible in practice because of friction
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