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rarefy

[rair-uh-fahy] /ˈrɛər əˌfaɪ/
verb (used with object), rarefied, rarefying.
1.
to make rare or rarer; make less dense:
to rarefy a gas.
2.
to make more refined, spiritual, or exalted.
verb (used without object), rarefied, rarefying.
3.
to become rare or less dense; become thinned:
Moisture rarefies when heated.
Origin
1350-1400
1350-1400; Middle English rarefien < Middle French rarefier < Latin rārēfacere, equivalent to rārē-, combining form of rārus rare1 (for expected rāri-; orig. of -ē- unclear) + facere to make; see -fy
Related forms
rarefiable, adjective
rarefier, noun
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for rarefy

rarefy

/ˈrɛərɪˌfaɪ/
verb -fies, -fying, -fied
1.
to make or become rarer or less dense; thin out
Derived Forms
rarefiable, adjective
rarefier, noun
Word Origin
C14: from Old French raréfier, from Latin rārēfacere, from rārusrare1 + facere to make
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Word Origin and History for rarefy
v.

late 14c., from Old French rarefier (14c.) and directly from Medieval Latin rarificare, from Latin rarefacere "make rare," from rarus "rare, thin" (see rare (adj.1)) + facere "to make" (see factitious). Related: Rarefied.

Online Etymology Dictionary, © 2010 Douglas Harper
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