o‧ver‧ac‧tive /ˌəʊvərˈæktɪv◂ $ ˌoʊv-/
adjective too active, in a way that produces a bad result
Antonym : underactive:
an overactive thyroid gland Such fears are nothing more than the product of an overactive imagination. [TahlilGaran] Dictionary of Contemporary English ▲