hyperactivePronunciation: /hʌɪpərˈaktɪv/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 behaviour. Derivatives hyperactively adverb hyperactivityPronunciation: /-ˈtɪvɪti/ noun hyperactive in other Oxford dictionaries Definition of hyperactive in the US English dictionary