Definition of Circle Game

What does the term "circle game" mean in the world of sports betting? What is the definition of the term "circle game" in the world of sports betting?

In sports betting, a "circle game" is a game where the sports book will lower the amount of money that a gambler can wager on a game. This is usually due to some sort of injury to one of the major players in the game or poor weather.

For instance - let's say that the New England Patriots are playing host to the Philadelphia Eagles. A few days before the game, Tom Brady breaks his foot and is ruled out of the game. A sports book may elect to lower the limits that people can wager on this game as a result, perhaps due to the fact that it will be hard to properly handicap the game thanks to people having little understanding as to how Brady's replacement will fare. In order to shield themselves from a potentially large loss, a sports book may reduce the amount of money that people can wager on the game.