rar·e·fac·tion noun \ˌrar-ə-ˈfak-shən, ˌrer-\
: the action or process of rarefying
: the quality or state of being rarefied; especially : an increase in porosity <areas of rarefaction in the bones>
: a state or region of minimum pressure in a medium transversed by compressional waves (as sound waves) <the eardrum vibrates according to the compressions and rarefactions of the sound wave>
—rar·e·fac·tion·al \-shnəl, -shən-əl\ adjective
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