Rarefaction

2 definitions found

From The Collaborative International Dictionary of English v.0.48 [gcide]:

  Rarefaction \Rar`e*fac"tion\ (r[a^]r`[-e]*f[a^]k"sh[u^]n), n.
     [Cf. F. rar['e]faction. See {Rarefy}.]
     The act or process of rarefying; the state of being rarefied;
     -- opposed to condensation; as, the rarefaction of air.
     [1913 Webster]



From WordNet (r) 2.0 [wn]:

  rarefaction
       n : a decrease in the density of something; "a sound wave causes
           periodic rarefactions in its medium"