The rectangular board behind a basketball hoop that the ball bounces off, or a board or backing material behind something for support.
From 'back' plus 'board.' Originally just any board that provides backing or support, but became standardized as a basketball term.
The basketball backboard is more important than people realize—without it, shots at angles wouldn't work because there'd be nothing to bounce the ball off. The backboard basically extends the 'goal' area and makes the game more forgiving and interesting than just swishing through a net.
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