0 used to refer to a type of betting (= risking money on horse races, sports games, etc.) that is done while the event is happening:
Most in-play backers were with Rafael Nadal.
With the in-running service, markets remain "live" while a sports event is in process.
The in-running punters depend on the scoreboards on respected tennis websites for match updates and stake their bets accordingly.
Those with access to in-running betting exchanges can afford to wait until after the flag falls.
A range of odds will be offered throughout the game so fans can bet in-play.
You can enjoy a bet before the action starts, or in-play at any point during the five days.