dyssynchrony noun4 •A lack of proper synchrony. •A medical condition wherein the activation of different parts of the heart is improperly synchronized. •A neurological condition wherein auditory stimuli are not processed synchronously. •A term created by Jean-Charles Terrassier in 1985 to define the disparity of a gifted child to his surroundings.External dyssynchrony refers to lack of natural fit between the gifted child and a school curriculum geared to average children of the same chronological age. — 1992 formsdyssynchronies