myosis n 1: an acute infectious disease occurring in epidemic form and featuring paroxysms of pain (usually in the chest) [syn: {epidemic pleurodynia}, {epidemic myalgia}, {diaphragmatic pleurisy}, {Bornholm disease}] 2: reflex contraction of the sphincter muscle of the iris in response to a bright light (or certain drugs) causing the pupil to become smaller [syn: {light reflex}, {pupillary reflex}, {miosis}] [also: {myoses} (pl)] myoses See {myosis}