Wiktionary
horseball
n. A sport played on horseback where points are scored by shooting a ball through a high net.
Wikipedia
Horseball
Horseball is a game played on horseback where a ball is handled and points are scored by shooting it through a hoop with a diameter of 1m. The sport is like a combination of polo, rugby, and basketball. It is one of the ten disciplines officially recognized by the International Federation for Equestrian Sports.