The act of dissociating or disuniting; a state of separation; disunion. It will add infinitely dissociation, distraction, and confusion of these confederate republics. Burke. The process by which a compound body breaks up into simpler constituents; -- said particularly of the action of heat on gaseous or volatile substances; as, the dissociation of the sulphur molecules; the dissociation of ammonium chloride into hydrochloric acid and ammonia.