The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

   2. Relief from toil or suffering: rest. [Obs.]
      [1913 Webster]

            Till the day
            Appear of respiration to the just
            And vengeance to the wicked.          --Milton.
      [1913 Webster]

   3. Interval; intermission. [Obs.] --Bp. Hall.
      [1913 Webster]

   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.
      [1913 Webster]

   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.
         [1913 Webster] 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.
         [1913 Webster]

WordNet (r) 3.0 (2006):

respiration
    n 1: the metabolic processes whereby certain organisms obtain
         energy from organic molecules; 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: respiration, 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, respiration, ventilation]

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "respiration":
   Aqua-Lung, artificial respiration, aspiration, asthmatic wheeze,
   breath, breath of air, breathing, broken wind, cough, exhalation,
   expiration, exsufflation, gasp, gulp, hack, hiccup, inhalation,
   inhalator, inspiration, insufflation, iron lung,
   mouth-to-mouth resuscitation, oxygen mask, oxygen tent, pant, puff,
   scuba, sigh, sneeze, sniff, sniffle, snore, snoring, snuff,
   snuffle, sternutation, stertor, suspiration, wheeze, wind



Bouvier's Law Dictionary, Revised 6th Ed (1856):

RESPIRATION, Med. jur. Breathing, which consists of the drawing into,
inhaling, or more technically, inspiring, atmospheric air into the lungs,
and then: forcing out, expelling, or technically expiring, from the lungs
the air therein. Chit. Med. Jur. 92 and 416, note n.