"To win the jackpot" means to be the lucky person who is chosen as the winner of a large cash prize in a game or a lottery. It is like hitting a big financial reward or achieving a major success. Full definition
I expect my odds of winning the jackpot in any lottery, multiple times in a row, are much better than picking the right god. (religion.blogs.cnn.com)
The extra prize money on offer will be as good as winning the jackpot on the new Gonzos Quest game from Net Entertainment! (justarsenal.com)
I've also found some loafers at the sale section for 9.90 $, it actually felt a bit like winning the jackpot as I found these babies in my size. (vogueetvoyage.com)