Chess boxing is just what it sounds like — a melding of boxing and chess that started as a fictional sport in comic books and film until fans decided to make the sport a reality and actually hold chess boxing bouts.
According to the Wikipedia entry on chess boxing,
A match consists of up to eleven alternating rounds of boxing and chess. The match begins with a four-minute chess round. This is followed by three minutes of boxing, with rounds of chess and boxing alternating until the end. There is a one minute break between rounds. Speed chess is used, a form in which each player has a total of only twelve minutes for the whole game.
Competitors may win by a knockout, achieving a checkmate, by the judges’ decision, or if their opponent’s twelve minutes of chess time is exceeded. If a competitor fails to make a move during the chess round, he is issued a warning and he must move within the next 10 seconds. Repeated warnings may result in a disqualification. The players put on headphones during the chess portion so that they do not hear any shouted assistance from the audience or the live chess commentary. If the chess game reaches a stalemate, the scores from the boxing rounds are used to determine the winner. If the boxing score is a tie, the player with the black pieces wins.
And yes, there is a World Chess Boxing Organization. God forbid Don King ever find out about this.