Goaltending is the violation that occurs when a defender touches the ball on its downward flight toward the basket or while it is on or above the rim.
Goaltending protects the shot at the end of its flight. Once a shot is descending toward the basket with a chance to score, or is sitting on or above the cylinder of the rim, a defender may not touch it. Do so and the basket is awarded as if it had gone in. The mirror image rule, basket interference, applies to offensive players touching a ball in the cylinder as well.
The rule exists because of giants. Players tall enough to camp at the rim and swat away descending shots, most famously the era of George Mikan and Bill Russell turning goaltending into a strategy, forced the sport to declare the end of a shot's flight sacred. Russell's genius was timing blocks on the way up, legally pinning shots before the descent began.
Modern replay has added border disputes: whether a shot had a real chance to score, whether a block came before the ball touched the backboard, a separate NBA trigger for goaltending, and whether a last second block saved or stole a game. Quiz questions about famous chases and blocks are secretly goaltending questions, decided by inches of downward flight.
In use"The block was waved off as goaltending, and the two points went on the board."