Behave honestly and honorably, obey the rules, as in Not every supplier we deal with plays fair, or We can't just leave them to find their own way back—that's not playing fair. Although this idiom conjures up playing by the rules in some game or sport, it actually has been used in this figurative way since the mid-1400s. Also see play the game.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
How to use play fair in a sentence
As you can imagine, this did not improve anyone's temper, or willingness to play fair.What if the Supreme Court Had Declined to Hear Bush v. Gore? | Megan McArdle | April 29, 2013 | THE DAILY BEAST
But I am not sure it will bring protection since this regime does not really play fair.
Can't play fair in a fight with a man half the size of one of you.The Highgrader | William MacLeod Raine
Now take the wheel and finish the watch; and next time play fair, and you won't have to work your passage.'Life On The Mississippi, Complete | Mark Twain (Samuel Clemens)
play fair with her; show her what your income is; give her all you can afford and what economic and wise administration warrants.Think | Col. Wm. C. Hunter