noun
decisive blow; finishing move
General term for a decisive action that settles a contest, argument, or situation. Used in sports, combat, and figurative contexts.
彼の一言が議論の決定打となった。
His single remark became the decisive blow in the argument.
ボクサーは最終ラウンドで決定打を放った。
The boxer landed the decisive blow in the final round.
noun
game-winning hit; clutch hit
Specifically in baseball, a hit that drives in the winning run or breaks a tie late in the game.
九回裏、彼のタイムリーが決定打となりチームは勝利した。
In the bottom of the ninth, his timely hit became the game-winner and the team won.
Compound of 決定 (decision, decisive) and 打 (hit, strike). The term likely originated in sports or martial contexts and extended to general decisive actions.