noun
1. : a sports rule adopted to modify play on a particular field, court, or course (as because of space limitations or the encroachment of spectators on a playing field)
if the backstop is less than 60 feet from home plate a ground rule will be necessary — Clement Wood & Gloria Goddard
2. : a rule of procedure or a principle of action specified for or intended to apply to a particular event or situation
having developed the primary purpose and general objectives of the company, a firm set of ground rules is therefore provided for the necessary detailed planning — C.F.Robinson
the first fundamental change in labor-relations ground rules in nearly twelve years — Time