running martingale

18 LETTERS · STARTS WITH R

running martingale is a valid 18-letter word worth 21 points in Scrabble and 30 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS

R1U1N1N1I1N1G2M3A1R1T1I1N1G2A1L1E1

1 + 1 + 1 + 1 + 1 + 1 + 2 + 0 + 3 + 1 + 1 + 1 + 1 + 1 + 2 + 1 + 1 + 1 =21 PTS

DOUBLE WORD → 42TRIPLE WORD → 63

MEANING

What does running martingale mean?