Real Dictionary

basketball
countable noun: A basketball is a large ball which is used in the game of basketball.
uncountable noun: Basketball is a game in which two teams of five players each try to score goals by throwing a large ball through a circular net fixed to a metal ring at each end of the court.

basketball in American English
a game played by two opposing teams of usually five players on a rectangular, often wooden, court with a raised basket at each end: points are scored by tossing a ball through the basket at the opponent's end
noun: a game played by two teams of usually five players each on a rectangular court having a raised basket or goal at each end, points being scored by tossing the ball through the opponent's basket

basketball in British English
noun: a game played by two opposing teams of five players each, usually on an indoor court. Points are scored by throwing the ball through an elevated horizontal metal hoop