\A`["e]r*a"tion\, n. [Cf. F. a['e]ration.]
1. Exposure to the free action of the air; airing; as,
   a["e]ration of soil, of spawn, etc.
2. (Physiol.) A change produced in the blood by exposure to
   the air in respiration; oxygenation of the blood in
   respiration; arterialization.
3. The act or preparation of charging with carbonic acid gas
   or with oxygen.