Gamesmanship is the use of dubious (although not technically illegal) methods to win or gain a serious advantage in a game or sport. It has been described as "Pushing the rules to the limit without getting caught, using whatever dubious methods possible to achieve the desired end" (Lumpkin, Stoll and Beller, 1994:92). It may be inferred that the term derives from the idea of playing for the game (i.e., to win at any cost) as opposed to sportsmanship, which derives from the idea of playing for sport. The term originates from Stephen Potter's humorous 1947 book, The Theory and Practice of Gamesmanship (or the Art of Winning Games without Actually Cheating).
Read more about Gamesmanship: Origins, Techniques, Football/soccer, Usage Outside of Games, The Gamesman Versus The Pure Player