also: のみこうい
noun
bookmaking; bucketing
Illegal gambling practice where a bookmaker or broker takes the opposite side of a customer's bet or order without actually executing it on an exchange. ノミ is a metaphor from a flea sucking blood, implying the operator 'sucks' the customer's money.
ノミ行為は法律で禁止されている。
Bookmaking is prohibited by law.
その証券会社はノミ行為で摘
That brokerage was busted for bucketing.
Refers to a legal bookmaker in contexts where sports betting is regulated; ノミ行為 is the illegal act itself, often associated with underground gambling.
Specifically refers to illegal private horse race betting tickets; ノミ行為 is a broader term covering various forms of illegal bookmaking and bucketing.
Compound of ノミ (flea) and 行為 (act). The flea metaphor suggests the operator 'sucks' the customer's money like a flea sucks blood. The exact origin is uncertain, but it is a well-established term in Japanese gambling and securities fraud contexts.