The term BALL CALLER refers to three different roles in sports: UMP (3 letters), REF (3 letters), and UMPIRE (6 letters). UMP stands for UMPIRE, which is the person responsible for making decisions on the field during a game. REF stands for referee, which is the person responsible for enforcing the rules of the game and ensuring fair play. UMPIRE stands for UMPIRE, which is the person responsible for making the final call on any disputed plays. All three roles are essential for a successful game.