1.
bookmaker; the house; gambling organizer; banker
The person or entity that organizes and runs a gambling operation, collecting bets and paying out winnings. By extension, can refer to the organizer or behind-the-scenes operator of any venture.
Originally from the world of gambling, where the 胴元 is the person who runs the game and takes a cut (寺銭) of all bets. In old gambling usage 胴 was the dealer's role (also 胴親), and 元 means source or owner. By extension, sometimes used figuratively to mean the behind-the-scenes organizer of any operation. Related: 賭博 (gambling — formal), 賭け事 (gambling — general), 寺銭 (the house's cut/commission).