From Longman Dictionary of Contemporary Englishhave a ballhave a ballinformalENJOY/LIKE DOING something to have a very good time → ball
Examples from the Corpus
have a ball• No matter where you go, what your interests, if you are into celebrating, you can have a ball.• Have dinner, have a ball, then spend the night, provided you have reservations.• He and I just have a ball.• The kids had a ball building sandcastles.• A playground and playhouse keep the tots happy while the teenagers have a ball with a whole host of absorbing activities.• Besides, to be really crass about it, the publicity people are going to have a ball with this.• We have a ball in my bag. 