Be highly successful, especially unexpectedly; win, especially a lot of money. For example, She hit the jackpot at the auction; that platter turned out to be genuine Meissen. This term comes from a form of poker in which a hand can be opened only if one holds at least a pair of jacks (or higher). Often a number of hands must be dealt before anyone can open, and since players must put in money for each round, the jackpot, or total amount held, is apt to be quite large. [Early 1900s]