No contest (abbreviated "NC") is a technical term used in some combat sports to describe a fight that ends for reasons outside the fighters' hands, without a winner or loser.
Rules in the United States now dictate that any bout which ends prior to the completion of the 4th round, due to an accidental headbutt, is to be declared a no contest.
Most other no contests in boxing occur when unusual circumstances, which would include instances such as an outdoor bout being rained out, the ring falling apart, or an unexpected injury caused by something outside of the boxer's control.
One good example of an unusual circumstance occurred in 1983, on the undercard of the fight where Roberto Durán beat Davey Moore for the World Jr. Middleweight title at the Madison Square Garden, when Luis Resto and Billy Collins Jr boxed ten rounds.
The injuries Collins received affected his sight, and, upon finding out what Resto and his corner had done, the New York State Athletic Commission decided to change the result of the fight to a no contest.
Maynard knocked himself temporarily unconscious during a takedown of Emerson, who then submitted due to an aggravated injury of the ribs, each being unaware that the other fighter could not continue.