A game-winning RBI (GWRBI) is a statistic that was used in Major League Baseball (MLB) from 1980 to 1988.[1] Building upon the run batted in (RBI) statistic, the game-winning RBI was defined in MLB rules as "the RBI that gives a club the lead it never relinquishes."
For example: A batter on the winning team brought his team ahead 3–2 from a 2–2 tie at some point during the game and his team later led 5–2 as a result of the other batters. Then, the opposing team scored two more runs, making the final score 5–4. The batter on the winning team who batted in the third run would be credited with the game-winning RBI, even though the losing team scored four runs. That the statistic "did not adequately distinguish the achievement it was meant to reward" was one of the criticisms that led to the statistic being retired.[2]
Statistically, the pitcher of the losing team who gives up the game-winning RBI is charged with a loss; the pitcher of the winning team who finished the last half-inning before the game-winning RBI is hit would be credited with the win (with certain exceptions).
Source: [3]