| A Battle Royal is a sort of racist's boxing match. Well, actually, at the time all boxing matches were racist, but anyway. In a Battle Royal you gather a group of young black men and have them duke it out (with or without gloves). The all-white spectators get to place bets and have a grand ol' time. The participants get to suffer minor to significant injury and one gets a prize. The prize being an unimpressive amount of money. During the "fights" there is some less than good natured ribbing of the particulars. Unless, of course, someone gets uppity.
You can read about a Battle Royal in Ralph Ellison's novel Invisible Man, which you should read anyway.
Also, as the links below already point out, Jack Johnson is said to have gotten his start in boxing this way. Of course, Johnson went on to be the most "uppity" black man of his day and took to beating the stuffing out of white men, getting rich, and then, sleeping with white women. | 
