1.
jackpot; big win
Winning a major prize in a lottery, raffle, or game of chance.
2.
big hit; great success
Something that turns out to be a great success, such as a product, movie, or restaurant choice.
Usage
大当たり is the emphatic form of 当たり (a hit/win). It can describe literal prize-winning or figurative success. It is commonly used in casual speech to express that something exceeded expectations.
Common collocations
Similar words
当たり means a regular win or hit, while 大当たり emphasizes a major, outstanding win. 大ヒット is used more for commercial or entertainment successes.