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.
胴元が一番儲かる。
The house profits the most.
違法な賭博の胴元が逮捕された。
The organizer of an illegal gambling operation was arrested.
ギャンブルでは最終的に胴元が得をするようにできている。
Gambling is structured so that the house ultimately comes out ahead.
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. The word comes from 胴 (the body of a dice cup) + 元 (origin/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).