This can be defined as the art of winning unfairly at sport without actually cheating. If a player profits from an unfair advantage, or covers up an unjust act, or intimidates his opponent/s by words or body language he is guilty of gamesmanship, which is the antithesis of good sportsmanship.
Unfortunately, histrionic questioning of line calls, hectoring and haranguing referees/umpires and taunting and goading opponents permeates all levels of professional sport, from tennis to football. It is scarcely surprising, therefore, that amateurs are aping the less attractive attitudes of the professionals, and bending the rules in order to win.
Any tendency to employ these tactics should be eradicated. Good manners in sport are paramount, as in other aspects of life. Even if this means you lose again and again, at least you will be doing it gracefully.