'walk-off' definitions:

Definition of 'walk-off'

From: GCIDE

walk-off \walk"-off`\, a. (Baseball) Game-ending and game-winning; such as to end the game immediately, and allow the players to walk off the field; -- of hits, especially home runs, which occur in the last half of the ninth or a later inning, which put the home team ahead of the visiting team and thereby end the game immediatey. This occurs in baseball because, when the last half of the ninth inning arrives, if the home team (which bats last) is already ahead in the score the last half of that inning is not played, the winner of the game having already been decided. Likewise, as soon as the home team gets ahead in the score after the visiting team has batted in the ninth inning, the game is ended. [Baseball jargon] [PJC]
Curtis's homer over the left-center-field fence beat the Braves and was the first walk-off homer by a Yankee in the World Series since Mickey Mantle slugged one against the St. Louis Cardinals in game 3 in 1964. --Jack Curry (New York Times, Oct.
28, 1999 p. D4) [PJC]
There are so many people in here who are happy for Chad. We know what he's been through. Those hits could make Chad Curtis's whole year. When you hit a walk-off homer in the World Series, that's something he's going to remember for a long time. --Paul O'Neill (the Yankee outfielder, quoted by Jack Curry in the New York Times, Oct.
27, 1999 p. D4) [PJC]