(horse racing) Any betting system in which all bets of a particular type are placed together in a pool; taxes and a house take are removed, and payoff odds are calculated by sharing the pool among all placed bets.
There is also a pari-mutuel option. You and a friend can wager that you will each lose 15 pounds over the next two months. If you both succeed, the money is returned. But if one fails while the other succeeds, then the loser pays the winner. If you both fail, then the one who loses the most is the winner.
A booth used to place such bets, or a machine used to record bets and calculate payoffs.