Definitions
American Heritage® Dictionary of the English Language, Fourth Edition
- n. A decrease in density and pressure in a medium, such as air, caused by the passage of a sound wave.
- n. The region in which this occurs.
Century Dictionary and Cyclopedia
- n. The act or process of rarefying or making rare, or of expanding or distending a body or mass of matter, whereby the bulk is increased, or a smaller number of its particles occupy the same space; also, the state or condition so produced: opposed to condensation. The term is used chiefly in speaking of gases, the terms dilatation and expansion being applied in speaking of solids and liquids. There was formerly a dispute as to whether rarefaction consisted merely of an increase in the mean distance of the particles (as it is now held to do), or in an enlargement of the particles themselves, or finally in an intrusion of foreign particles. In the strictest sense, the word was understood to signify the second action.
Wiktionary
GNU Webster's 1913
- n. The act or process of rarefying; the state of being rarefied; -- opposed to
condensation .
WordNet 3.0
- n. a decrease in the density of something
Examples
“But if, for example, the rise in the emulsion to double the rarefaction is a milliard times less than in oxygen, it means that the effective weight of the grain is a milliard times greater than that of the oxygen molecule.”
“He is also studying the process of rarefaction, which is when capillaries and vessels start losing their density.”
“Instead, they used a theoretical approach called rarefaction for gene discovery, a process developed for ecological surveys to determine the abundance of a species in an ecosystem.”
“Such quantity, however, should not be identified with the determinate dimensions a body possesses, but is rather a quantitas which remains the same during processes such as rarefaction and condensation.”
“When it comes to estimating how many species are yet to be discovered, Webb says scientists use a technique called "rarefaction": "Imagine a garden pond.”
“The Dictionary of Islam by Thomas Patrick Hughes states: “They become invisible at please (by a rapid extension or rarefaction of the particles which compose them), or suddenly disappear in the earth or air, or through a solid wall.””
“Boyle suggested that the divergence from the expected result in the case of rarefaction may have been due to "some little aerial bubbles in the quicksilver" ( "so easy is it in such nice experiments to miss of exactness," he added).”
“The results are set out, with misprints, in two tables, and Boyle's conclusion was that the experimental findings matched the predicted results very well in the case of compression, less well in the case of rarefaction.”
“This move becomes evident in certain physical questions, e.g., in the study of condensation and rarefaction, where Albert openly disagrees with his Parisian master by arguing that condensation and rarefaction are possible only through the local motion of the parts of a body, and without needing to assume some quantity that would have a distinct reality on its own.”
“He calls her feminine because he has no better word: the feminine, a higher rarefaction of the female, to the point of becoming spirit.”
Lists
These user-created lists contain the word ‘rarefaction’.
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A Rarefaction of Factoids
List of genuine words and phrases containing the string fact-, -fact-, or -fact. Beginning with ventifact and stupefaction.
ventifact, stupefaction, fact, factoid, rarefaction, unsatisfactory, satisfactory, tumefaction, surfactant, artifact, benefactor, benefaction and 142 more...
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Not 250 Spelling Words Again
Yet more spelling words for intermediate to advanced spellers.
kyoodle, heimin, feis, menarche, cordwainer, gherao, zythum, accidie, anastomosis, boustrophedon, oleum, penicillin and 238 more...
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There's a word for it
catkin, pastiche, badonkadonk, biome, omphaloscopy, pogonophobia, reptation, anathema, xyst, commodify, commoditize, monetize and 68 more...
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Specificity
Words that have with subtly different meanings from other words.
vestibule, commoditize, commodify, monetize, corroborate, mezzanine, apposite, irony, calefacient, maxim, pandiculate, rarefaction and 39 more...
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gcherches's Words
serendipity, roadrunner, inner child, coagulant, esquire, vicissitude, idiot savant, mitigation, affirmation, affirmative, diatribe, affirmative action and 185 more...
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ivancapistrano's list
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tranquill's Words
loquacious, unmitigated, trundle, ephemeral, vociferous, trapezoidal, liminal, obsequious, veracity, squash, onomatopoeia, oscillate and 267 more...
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rememberers
prolix, ageusia, animadversion, anodyne, antic, arabesque, beadle, brachymetropia, colophon, desquamation, diaphoresis, diegesis and 3248 more...
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Useful Words
I can use these.
aptronym, haplology, ectopia, folderol, volute, caryatid, spandrel, pendulous, miasmic, gelid, dotty, anomie and 256 more...
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Tip of my tongue
I tend to find myself searching for these words.
insinuate, schwag, coquette, mezzanine, affront, tacit, tantamount, nascent, wisteria, assuage, epistolary, impinge and 38 more...
Tweets
Looking for tweets for rarefaction.

fbharjo I unda-stand! Its a rare density and/or a dense rarity! Meracious (untruth) fingere! Oct 8, 2011
leaden “I do not know,” he began, “if you have ever considered the nature of sound. Suffice to say that it consists of a series of waves moving through the air. Not, however, waves like those on the surface of the sea — oh dear no! Those waves are up and down movements. Sound waves consist of alternate compressions and rarefactions.”
“Rare-what?”
“Rarefactions.”
“Don’t you mean ‘rarefications’?”
“I do not. I doubt if such a word exists, and if it does, it shouldn’t,” retorted Purvis, with the aplomb of Sir Alan Herbert dropping a particularly revolting neologism into his killing-bottle. . . .
— Arthur C. Clarke. “Silence, Please”. Oct 8, 2011