Respiratory \Re*spir"a*to*ry\ (r?*sp?r"?*t?*r? or r?s"p?*r?-), a. (Physiol.) Of or pertaining to respiration; serving for respiration; as, the respiratory organs; respiratory nerves; the respiratory function; respiratory changes. {Respiratory foods}. (Physiol.) See 2d Note under {Food}, n., 1. {Respiratory tree} (Zo["o]l.), the branched internal gill of certain holothurians.