Longman Dictionary of Contemporary English
Wiktionary
n. (ground rule English)
Wikipedia
In baseball, ground rules are special rules particular to each baseball park (grounds) in which the game is played. Unlike the well-defined playing field of most other sports, the playing area of a baseball field extends to an outfield fence in fair territory and the stadium seating in foul territory. The unique design of each ballpark, including fences, dugouts, bullpens, railings, stadium domes, photographer's wells and TV camera booths, requires that rules be defined to handle situations in which these objects may interact or interfere with the ball in play or with the players.
Major League Baseball has defined a set of "universal ground rules" that apply to all MLB ballparks; individual ballparks have the latitude to set ground rules above and beyond the universal ground rules, as long as they do not directly contradict each other. Additionally, a set of universal ground rules exists for the six MLB stadiums with retractable roofs, with the individual ballparks able to set additional rules.
The term ground rule double is often applied to a batted ball that bounces fair, then over the outfield fence in fair or foul territory, although some commentators and writers shun the term because league-wide rules, not ground rules, apply in this case.
Usage examples of "ground rules".
Eliot got his training from Auton, who helped to establish the ground rules for modern espionage.
Over the years, she had established her own ground rules, and had become a good judge of those likely to share her values and attitudes.
Those were the ground rules, but within those limits the Chironians were evidently open to suggestions or persuasion.
Really, she was going to drive him bonkers if he didn't set a few ground rules.