The result of a "double or nothing" bet is either cancellation of a debt or the doubling of a debt.
[2][3][4][5] It can be seen as a gentleman's agreement which grants losers of an initial bet a chance to win their money back, with minimal risk to the winner.
In poker, a double or nothing tournament is a sit'n'go tournament where half of the surviving players get double the buy-in and the eliminated half does not receive any prizes.
Some poker rooms also offer triple or nothing tournaments, where one-third of the playing field gets paid.
Not to be confused with "doubling down" in blackjack.