"Ref" is a commonly used abbreviation for "referee", which is a professional who officiates sports or competitions and enforces the rules and regulations. As such, some synonyms for "ref" would include "umpire", "judge", "official", "arbitrator", or "referee". These words typically refer to a person or group of people who watch, manage or control various sports, games, or events, keeping them fair and in compliance with the rules. The choice of synonym used is often based on context, industry, and location where the game is played, and can also help to create variety and interest in communication.