hyperactive Syllabification: (hy·per·ac·tive)Pronunciation: /ˌhīpərˈaktiv/Translate hyperactive | into French | into German | into Italian | into Spanish Definition of hyperactive adjective abnormally or extremely active:a hyperactive pituitary gland (of a child) showing constantly active and sometimes disruptive behavior. Derivatives hyperactivityPronunciation: /-ˌakˈtivitē/ noun hyperactive in other Oxford dictionaries Definition of hyperactive in the British & World English dictionary