: a notably powerful, prominent, or important person or organization
James Carville was seen dining at The Palm with 20 or so other big hitters who were avoiding the balls, which had underwhelmed them the last time. Eric Konigsberg, Vogue, March 1997
I hired another senior account supervisor who was a really big hitter. Charles Tentrick, Lessons From the Edge, 2003
Madoff was a big hitter so you'd expect him to be using a big hitter's accounting firm to conduct audits and verify his accounts. Jeffrey Robinson, Revelation of Audacious Frauds, Scams, and Cons, 2010