noun (n)

• the act of supplying fresh air and getting rid of foul air(noun.act)

  Synonym:
  airing
  

  source: wordnet30
• a mechanical system in a building that provides fresh air(noun.artifact)

  Example:
  She was continually adjusting the ventilation.
  

  Synonym:
  ventilating system, ventilation system
  

  source: wordnet30
• free and open discussion of (or debate on) some question of public interest(noun.communication)

  Synonym:
  public discussion
  

  source: wordnet30
• the bodily process of inhalation and exhalation; the process of taking in oxygen from inhaled air and releasing carbon dioxide by exhalation(noun.act)

  Synonym:
  breathing, external respiration, respiration
  

  source: wordnet30
• 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.(noun)

  source: webster1913