rebate shop
n.— «He bets through what are called rebate shops, which are off-shore, on Indian reservations or in states with fewer regulations. Rebate shops offer from 4 percent to 10 percent back on every dollar wagered—win or lose.» —“Horse Racing’s Biggest Bettors Are Reaping Richest Rewards” by Joe Drape New York Times Apr. 26, 2004. (source: Double-Tongued Dictionary)