from
The Collaborative International Dictionary of English v.0.48
Jackpot \Jackpot\, n.
1. Same as {jack pot}. See under {jack}.
[PJC]
2. Any larger-than-usual gambling prize formed by the
accumulation of unwon bets.
[PJC]
3. The highest gambling prize awarded in a gambling game in
which smaller prizes are also awarded, especially such a
prize on a slot machine.
[PJC]
4. An unusually large success in an enterprise, either
unexpected or unpredictable, esp. one providing a great
financial benefit.
[PJC]
{hit the jackpot} to receive an unexpectedly large (or the
largest possible) benefit from an enterprise; as, after
prospecting for years, he finally hit the jackpot when he
discovered a silver lode.
[PJC]