Respiration definition
Definition of RESPIRATION for Kids. 1. : the act or process of breathing: the inhaling of oxygen and the exhaling of carbon dioxide. 2. : the process by which cells use oxygen to break down sugar and obtain energy.ull Definition of RESPIRATION. 1. a: the placing of air or dissolved gases in intimate contact with the circulating medium of a multicellular organism (as by breathing) b: a single complete act of breathing.