From Longman Dictionary of Contemporary Englishheavy hitterˌheavy ˈhitter noun [countable] American English 1 POWERa person or company that has a lot of power, especially in business or politics2 DSBa baseball player who hits the ball very hard
Examples from the Corpus
heavy hitter• The issue has drawn the attention of some of Hollywood's heavy hitters.From Longman Business Dictionaryheavy hitterˌheavy ˈhitter noun [countable] informal journalism a person or organization with a lot of influence or powerWe wanted a heavy hitter as chairman. 