The Collaborative International Dictionary of English v.0.48:

Ventilation \Ven`ti*la"tion\, n. [L. ventilatio: cf. F.
   ventilation.]
   1. The act of ventilating, or the state of being ventilated;
      the art or process of replacing foul air by that which is
      pure, in any inclosed place, as a house, a church, a mine,
      etc.; free exposure to air.
      [1913 Webster]

            Insuring, for the laboring man, better ventilation.
                                                  --F. W.
                                                  Robertson.
      [1913 Webster]

   2. The act of refrigerating, or cooling; refrigeration; as,
      ventilation of the blood. [Obs.] --Harvey.
      [1913 Webster]

   3. The act of fanning, or winnowing, for the purpose of
      separating chaff and dust from the grain.
      [1913 Webster]

   4. The act of sifting, and bringing out to view or
      examination; free discussion; public exposure.
      [1913 Webster]

            The ventilation of these points diffused them to the
            knowledge of the world.               --Bp. Hall.
      [1913 Webster]

   5. The act of giving vent or expression. "Ventilation of his
      thoughts." --Sir H. Wotton.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ventilation
    n 1: the act of supplying fresh air and getting rid of foul air
         [syn: ventilation, airing]
    2: a mechanical system in a building that provides fresh air;
       "she was continually adjusting the ventilation" [syn:
       ventilation, ventilation system, ventilating system]
    3: free and open discussion of (or debate on) some question of
       public interest; "such a proposal deserves thorough public
       discussion" [syn: public discussion, ventilation]
    4: 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:

67 Moby Thesaurus words for "ventilation":
   aerage, aeration, air conditioning, air cooling, airing, analysis,
   bandying, book, broadcast, broadcasting, bruiting, bruiting about,
   buzz session, canvassing, circulation, colloquium, confabulation,
   conference, consideration, cross-ventilation, debate, debating,
   deliberation, deodorization, deodorizing, dialectic, dialogue,
   diffusion, discussion, display, dissemination, evulgation,
   examination, exchange of views, forum, fumigation, investigation,
   issuance, issue, joint discussion, logical analysis,
   logical discussion, open discussion, open forum, oxygenation,
   oxygenization, panel discussion, perflation, periodical, printing,
   promulgation, propagation, publication, publishing, rap,
   rap session, refreshment, review, seminar, spread, spreading,
   spreading abroad, study, symposium, telecasting, town meeting,
   treatment