sudden death

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Extra play added to determine the winner of a tied game, often with the victory awarded to the first to score.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Instantaneous, unexpected death not caused by violence.
• noun sports The climax of a game, in which the next team to score instantly wins; often in an extra period of time following a tie at the end of the regular period of play.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (sports) overtime in which play is stopped as soon as one contestant scores; e.g. football and golf