Battle royal is a tournament structure in which competitors are not assigned specific opponents or times to play. Instead they seek out and challenge other competitors and attempt to eliminate them or improve their own standing.
This format is uncommon in the real world, but has been used a number of times in the anime and manga. In the Duelist Kingdom, Battle City, Genex and World Duel Carnival tournaments, players were given items, Star Chips, Locator Cards, Genex Medallions and Heart Pieces respectively. Players had to wager these items on each Duel they played. If they ran out of items they were eliminated. In Duelist Kingdom, Battle City and the World Duel Carnival, they needed to collect a certain number of these items to qualify for the final stages of those tournaments. In the Genex Tournament, one player had to win all the medallions to be declared the winner.