godan verb (-ru), transitive verb
hit repeatedly; pound away; unleash a barrage
Used for striking something many times in quick succession, whether physically (punching, hitting a ball) or figuratively (typing furiously). Often implies energetic, continuous action.
彼はキーボードを打ちまくって、一晩でレポートを書き上げた。
He pounded away at the keyboard and finished the report in one night.
ボクサーは相手
The boxer unleashed a barrage of blows to his opponent's face.
昨日の試合で、彼はヒットを打ちまくった。
In yesterday's game, he belted hit after hit.