ground rule noun

1. ground rules
   [plural] the basic rules on which something is based
   • ● The new code of conduct lays down the ground rules for management-union relations.
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2. [countable] (North American English, sport) a rule for the playing of a game on a particular field, etc.Topics

[TahlilGaran] English Dictionary ▲

ground rule
n.
1. A rule in sports that is made especially for the grounds or place where a game is played.
■ Usually used in the plural.
There was such a big crowd at the baseball game, that the ground rules of the field were changed in case a ball went into the crowd.
2. A rule, usually not written, of what to do or how to act in case certain things happen.
■ Usually used in the plural.
When you go to a new school, you don't know tire ground rules of how you are supposed to behave.

[TahlilGaran] English Idioms Dictionary ▲