from
The Collaborative International Dictionary of English v.0.48
Martingale \Mar"tin*gale\, Martingal \Mar"tin*gal\, n. [F.
martingale; cf. It. martingala a sort of hose, martingale,
Sp. martingala a greave, cuish, martingale, Sp. alm['a]rtaga
a kind of bridle.]
1. A strap fastened to a horse's girth, passing between his
fore legs, and fastened to the bit, or now more commonly
ending in two rings, through which the reins pass. It is
intended to hold down the head of the horse, and prevent
him from rearing.
[1913 Webster]
2. (Naut.) A lower stay of rope or chain for the jib boom or
flying jib boom, fastened to, or reeved through, the
dolphin striker. Also, the dolphin striker itself.
[1913 Webster]
3. (Gambling) The act of doubling, at each stake, that which
has been lost on the preceding stake; also, the sum so
risked; -- metaphorically derived from the bifurcation of
the martingale of a harness. Called also {Martingale
strategy}. Such a betting strategy does not change the
overall likelihood of winning, but in a short run it
increases the probability of winning a small sum,
balancing it against an increased probability of losing a
large sum. [Cant] --Thackeray.
[1913 Webster +PJC]