sudden death 
noun [mass noun] informal
A means of deciding the winner in a tied match, especially one in which the first side or player to concede a game, goal, or point during an additional period of play is the loser: [as modifier]: a sudden-death play-off...
- The runners-up, and the best third placed team, will then play sudden-death play-off games to decide the three other clubs in the quarter-finals.
- They had also survived a tense semi-final against Russia, Turnbull scoring a try in sudden-death extra-time.
- This is especially true in the play-offs, when sudden-death overtime adds to the fatigue and makes this time of the year so special.