Cheating was the act of playing a game dishonestly with the objective of winning without having to play by the rules.
When the Toymaker used his own cards in his and the Fourteenth Doctor's game of Cut in 1925 Soho, Donna Noble believed he was going to cheat until the idea was shut down by both the Doctor and the Toymaker, whom showed offence at the notion, with the Doctor explaining that the Toymaker had to follow the rules of the game because they bound his existence. Indeed, the Toymaker ended up making an honest victory in their game when he drew the higher card.
When they faced each other in their third game atop the UNIT headquarters in 2023 London, the Toymaker claimed that the Fourteenth and Fifteenth Doctors were cheating when both of them challenged him to a game at the same time, only for the Doctors to point out that they were both the same person, and also pointed out the Toymaker's fault in the bi-generation that "doubled" them, causing him to relent and play against both of them. However, he tried to give himself an early advantage in their game of catch by lobbing the ball at the Fourteenth Doctor unexpectedly, though the Doctor managed to catch it. (TV: The Giggle [+]Russell T Davies, Doctor Who 60th Anniversary Specials (BBC One and Disney+, 2023).)
When Maestro at first refused to tell the Fifteenth Doctor how she had entered the Earth, he complained that her father, the Toymaker, had established the rules of fair play and that the one thing he would never do was cheat, thus he had the right to know. (TV: The Devil's Chord [+]Error: Code 2 - no data stored in variables, cache or SMW.)