To act, behave, or play fairly and justly; to observe the rules or the laws; to not cheat or betray the spirit of something. Often used in negative formations. If you don't play fair, no one is going to want to play games with you anymore! The watchdog accused the giant multinational corporation of not playing fair with its tax obligations. Everyone I know cheats the system to their advantage, so why should I have to be the one to play fair?