The term 'shot caller' is a slang term used to describe someone who is in charge of making decisions and giving orders. The crossword solutions for this term are REF, which stands for referee. A referee is an official who enforces the rules of a game or sport, and is responsible for making sure that the game is played fairly. They also have the authority to make decisions and give orders during the game. Therefore, the term 'shot caller' can be used to describe a referee, as they are in charge of making decisions and giving orders.