Martingales

noun

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