Source : Webster's Revised Unabridged Dictionary (1913)

Rarefy \Rar"e*fy\, v. t. [imp. & p. p. {Rarefied}; p. pr. & vb.
   n. {Rarefying}.] [F. rar['e]fier; L. rarus rare + -ficare (in
   comp.) to make; cf. L. rarefacere. See {-fy}.]
   To make rare, thin, porous, or less dense; to expand or
   enlarge without adding any new portion of matter to; --
   opposed to condense.

Source : WordNet®

rarefied
     adj 1: having low density; "rare gasses"; "lightheaded from the
            rarefied mountain air" [syn: {rare}, {rarified}]
     2: reserved for an elite group [syn: {rarified}]
     3: of high moral or intellectual value; elevated in nature or
        style; "an exalted ideal"; "argue in terms of high-flown
        ideals"- Oliver Franks; "a noble and lofty concept" [syn:
        {exalted}, {high-flown}, {high-minded}, {lofty}, {rarified},
         {idealistic}, {noble-minded}]

rarefy
     v 1: lessen the density or solidity of; "The bones are rarefied"
     2: make more subtle or refined [syn: {sublimate}, {subtilize}]
     3: weaken the consistency of (a chemical substance) [syn: {attenuate}]
     [also: {rarefied}]

rarefied
     See {rarefy}