(1) (physiology) Breathing; the exchange of air between lungs and outside air; the inhalation and exhalation of air; the process of taking in oxygen from the air that enters the lungs through inhalation and releasing of carbon dioxide through exhalation
(2) (psychiatry) Verbalization of emotional problems
(3) (general) The system of replacing fresh air for noxious or spent air
Pulmonary ventilation may take place naturally, mechanically, or artificially. In general, a person at rest typically breathes and exhales air, at a rate of five to six liters per minute.