1. The process of becoming light or less dense; the condition of being light; opposed to condensation. 2. In vascular physiology, the process that results in a reduction in the density of capillaries in a tissue. [L. rarus, thin, scanty + facio, to make]
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rar·e·fac·tion .rar-ə-'fak-shən, .rer- n
1) the action or process of rarefying
2) the quality or state of being rarefied esp an increase in porosity <areas of \rarefaction in the bones>
3) 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 adj
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n.
thinning of bony tissue sufficient to cause decreased density of bone to X-rays, as in osteoporosis.
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rar·e·fac·tion (rar″ə-fakґshən) [L. rarefactio] the condition of being or becoming less dense; diminution in density and weight, but not in volume.Medical dictionary. 2011.