IPA: //ˈdʒækpɒt//
KK: /ˈdʒækpɑt/
A large prize or amount of money that is won in a game, lottery, or competition, often after a long period of accumulation.
Winning the jackpot in the lottery changed her life forever.
Jackpot is formed from "jack" (a term used in various games, possibly derived from the name of a common playing card or a slang term for a man) and "pot" (from Old French *pot*, meaning a container or vessel). The term originally referred to a large prize in a game, particularly in gambling contexts, where the 'pot' is the accumulated stakes.
Think of 'jack' as a player in a game and 'pot' as the container holding the prize — together, they remind you that a jackpot is the big prize in a game.