martingale

noun

1. A piece of harness used on a horse to keep it from raising its head above a desired point.

   “I’ll be bound, Lady Ashton understands every machine for breaking in the human mind, and there are as many as there are cannon-bit, martingales, and cavessons for young colts.”

2. A spar, or piece of rigging that strengthens the bowsprit.
3. A stochastic process for which the conditional expectation of future values given the sequence of all prior values is equal to the current value.

   “If a gambler plays a fair game repeatedly, his payoff over time is a martingale.”

4. A gambling strategy in which one doubles the stake after each loss.
5. A strap attached to the sword handle, preventing a sword being dropped if disarmed.

verb

1. To employ the martingale strategy in gambling.

   “The Russians were both martingaling it—doubling their bets when they lost.”