1 general:: Enjoy oneself enormously, as in It was a great trip? I had a ball. This idiom uses the noun ball in the sense of "a gala dance." [Slang; 1920s]
American Heritage Idioms
2 general:: Phrase(s): have a ball to have an exciting time. • I plan to have a ball while I’m on vacation. • Come on, everybody! Let’s have a ball!
McGrawhill's American Idioms And Phrasal Verbs