What is the meaning of ventilation?

noun

• The act of supplying fresh air and getting rid of foul air.
  • synonyms: airing
• A mechanical system in a building that provides fresh air.
  • usage: "she was continually adjusting the ventilation"
  • synonyms: ventilation system, ventilating system
• Free and open discussion of (or debate on) some question of public interest.
  • usage: "such a proposal deserves thorough public discussion"
  • synonyms: public discussion
• The bodily process of inhalation and exhalation; the process of taking in oxygen from inhaled air and releasing carbon dioxide by exhalation.
  • synonyms: breathing, external respiration, respiration