martingal

noun

1. the strap of a horse's harness passing from the noseband to the girth between the forelegs, to keep the horse from rearing or throwing back its head
2. 1. a lower stay for the jib boom or flying jib boom of a sailing vessel, to bear the strain of the head stays
   2. dolphin striker
3. a system of betting in which, after a losing wager, the amount bet is doubled or otherwise increased