The term 'flag thrower, at times' can be abbreviated as 'REF' in a crossword puzzle. A referee is an official who enforces the rules of a sport or game. They are responsible for making sure that the players abide by the rules and regulations of the game. Referees also have the authority to issue penalties or warnings to players who break the rules. Flag throwers, at times, are referees who throw a flag when they observe a violation of the rules. This is usually done to signal a penalty or to stop play.