The Rice University Neologisms Database

To repeatedly score points during basketball with few to no missed shots. This term is commonly used among the lingo of streetball players. When someone is raining shots, it signifies that he or she is consecutively making shots without missing any baskets. The term could be associated with how rain continuously pours down water, and when a player is raining, he or she is pouring down shots. This term has a good connotative association; it suggests that the player is exceptionally talented in the game, and the team depends on him/her. If the player is arrogant in his game, even if he /she is good, “rainmaker” (the noun form for someone that can call upon the rain – in basketball, someone that you can count on to make the shots) will not be label he / she gets. Instead, “ballhog” is the term for the overconfident player. The origin of the word “rain” is ambiguous.