noun
loose ball; rebound
Sports term for a ball that comes free during play, often after a missed shot or a fumble, available for either team to recover.
シュートが外れてこぼれ球を相手に拾われた。
The shot missed and the loose ball was picked up by the opponent.
こぼれ球に素早く反応してゴールを決めた。
He reacted quickly to the rebound and scored a goal.
リバウンド is a loanword from English 'rebound', often used in basketball for a rebound off the backboard or rim. こぼれ球 is a native Japanese term used more broadly in sports like soccer or rugby for any loose ball.
Compound of こぼれ (continuative form of こぼれる 'to spill, to fall out') and 球 (たま 'ball'). Literally 'spilled ball'.