noun
win by opponent's foul; victory due to a foul
Used in sports contexts when a competitor wins because the opponent committed a foul or violation.
ボクシングで相手の反則により反則勝ちになった。
He won by opponent's foul in boxing due to the opponent's violation.
反則負け means a loss due to one's own foul, while 反則勝ち is a win due to the opponent's foul.
Compound of 反則 (foul, violation) and 勝ち (win, victory).