1. Usually, ground rules. basic or governing principles of conduct in any situation or field of endeavor: the ground rules of press conferences.
2. Sports.any of certain rules specially adopted, as in baseball and softball, for dealing with situations or circumstances arising chiefly from the particular nature of the playing area or the interference of spectators.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.