外そと馬うま

noun

side bet matching a player's wins/losses

In mahjong, a spectator's bet that mirrors the point gains and losses of a specific player. Not a standard gambling term outside mahjong.

• 彼かれは友とも達だちの対たい局きょくに外そと馬うまを張はって、一いっ喜き一いち憂ゆうしていた。

  He placed a side bet on his friend's game and went through ups and downs with every hand.