Tiebreaker (noun)

1. A method or event used to determine a winner in a tied competition, match or game.
2. Something that serves to resolve a tied situation or equal balance.

Origin:

First recorded in 1960-65, from tie + breaker.

Examples:

1. The tiebreaker was a sudden-death penalty shootout.
2. The tennis match was decided by a tiebreaker in the third set.
3. A coin flip was used as a tiebreaker to determine who would start the game.
4. The two candidates were neck-and-neck in the polls, so the debate became a key tiebreaker for many voters.
5. The company's tiebreaker policy for equal bids is to award the contract to the bidder with the best customer service record.