Source : Webster's Revised Unabridged Dictionary (1913)

Respiration \Res`pi*ra"tion\ (r?s`p?*r?"sh?n), n. [L.
   respiratio: cf. F. respiration. See {Respire}.]
   1. The act of respiring or breathing again, or catching one's
      breath.

   2. Relief from toil or suffering: rest. [Obs.]

            Till the day Appear of respiration to the just And
            vengeance to the wicked.              --Milton.

   3. Interval; intermission. [Obs.] --Bp. Hall.

   4. (Physiol.) The act of resping or breathing; the act of
      taking in and giving out air; the aggregate of those
      processes bu which oxygen is introduced into the system,
      and carbon dioxide, or carbonic acid, removed.

   Note: Respiration in the higher animals is divided into:
         ({a}) Internal respiration, or the interchange of
         oxygen and carbonic acid between the cells of the body
         and the bathing them, which in one sense is a process
         of nutrition. ({b}) External respiration, or the
         gaseous interchange taking place in the special
         respiratory organs, the lungs. This constitutes
         respiration proper. --Gamgee. In the respiration of
         plants oxygen is likewise absorbed and carbonic acid
         exhaled, but in the light this process is obscured by
         another process which goes on with more vigor, in which
         the plant inhales and absorbs carbonic acid and exhales
         free oxygen.

Source : WordNet®

respiration
     n 1: the metabolic processes whereby certain organisms obtain
          energy from organic moelcules; processes that take place
          in the cells and tissues during which energy is released
          and carbon dioxide is produced and absorbed by the blood
          to be transported to the lungs [syn: {internal
          respiration}, {cellular respiration}]
     2: a single complete act of breathing in and out; "thirty
        respirations per minute"
     3: the bodily process of inhalation and exhalation; the process
        of taking in oxygen from inhaled air and releasing carbon
        dioxide by exhalation [syn: {breathing}, {external
        respiration}, {ventilation}]