<p><strong>Noun</strong></p><ul><li>the act of respiring; inhalation and exhalation of air; breathing</li><li>Biology: the sum total of the physical and chemical processes in an organism by which oxygen is conveyed to tissues and cells, and the oxidation products, carbon dioxide and water, are given off</li><li>an analogous chemical process, as in muscle cells or in anaerobic bacteria, occurring in the absence of oxygen</li></ul>