A type of home run that occurs when the batter hits a home run that ends the game by putting their team in the lead. For a Walk-off Home Run to occur, it needs to happen during the bottom of one of the final innings of the game either the ninth inning or an extra inning. It's referred to as a Walk-off Home Run because both teams "walk-off" the field because the game is over.
Walk-off Home Runs are fairly dramatic due to their abrupt nature as they effectively end the game immediately. There have been a few very dramatic Walk-off Home Runs including two World Series clinching home runs.
In 1960, Pittsburgh Pirates Bill Mazeroski was the lead off hitter in the 9th inning facing Ralph Terry of the New York Yankees with the game tied at 9-9 and the series at 3-3, Mazeroski hit a home run on the first pitch to win the series for the Pirates. In 1993, Joe Carter of the Toronto Blue Jays eliminated the Philadelphia Phillies with a three run Walk-off Home Run to clinch the teams second straight World Series.