I didn't see what you were looking for.. The technical definition does come from BlackJack. If you are comfortable that you can win on the next card draw, you can call for a double down. This means you are doubling your bet amount, and you draw *exactly* 1 more card. In slang terms, when you are doubling down, you are "gambling"/asserting that your position is correct, and that you are comfortable with any possible risk. David F.