Rarefy /(răr"ē̇*fī; 277)/

Rar·e·fy

Rarefy

v. t.

imp. & p. p. Rarefied; p. pr. & vb. n. Rarefying

  1. To make rare, thin, porous, or less dense; to expand or enlarge without adding any new portion of matter to; -- opposed to condense.

Rarefy

v. i.
  1. To become less dense; to become thin and porous.