American Heritage® Dictionary of the English Language, Fourth Edition
- n. The hypothetical continuous operation of an isolated mechanical device or other closed system without a sustaining energy source.
- n. The motion of some hypothetical device that continues forever with no obvious input of energy in violation of the laws of thermodynamics.
GNU Webster's 1913
- n. (Mech.) 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.
- adj. See under Motion.
- n. motion that continues indefinitely without any external source of energy; impossible in practice because of friction
“Now, that perpetual motion of rotation seems to be proper to the heavenly bodies, station or rest seems to belong to the globe of the earth, while other bodies (which they call heavy or light, being indeed placed out of the region to which they naturally belong) are carried toward the masses or congregations of their likes; light bodies upward toward the circumference of the heaven, heavy bodies downward towards the earth.”
“Medieval and Renaissance perpetual motion ma - chines, indeed machines in general, were characterized by an exuberant delight in elaboration: gear trains were added merely for the sake of complexity as well as in the hope of hitting on a more subtle science of mechanics that would transcend mere earthbound me - chanics.”
“Then there was Miss B., an independent, good-natured, do-as-I-please sort of a body, who seemed of perpetual motion from morning till night.”
“Olivet's eyes stopped their perpetual motion and bored into the Saint.”
“The wine, the coruscating heat of the sun and the mitigating balm of the breeze, the smell of aloes, the rousing choruses, the ever-incredible nakedness of the girls, the Morse code of virgin light glancing after the perpetual motion of the waters, conspired together and unknitted the dry bones in his heart.”
“The quest for perpetual motion was abandoned, for the logical implication of the concept of efficiency is that restoration, or recov - ery, of the initial situation is the utmost that can be expected even of an ideal engine.”
“By the perpetual motion of the royal camp, each province was successively blessed with his presence; and he is said to have perambulated twelve times the wide extent of his dominions, which surpassed the”
“The last aspect of medieval and Renaissance technics that we shall mention was the proliferation of attempts to devise a perpetual motion machine.”
These user-created lists contain the word ‘perpetual motion’.
Inspired by the definition of idiot's delight. I'm sure we can come up with some pretty inspired (and not necessarily mean-spirited) additional definitions.
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Words I keep forgetting.
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