ref
n. countable B1 Intermediate US //ˈɹɛf// UK //ɹˈɛf// ref
n. the person who makes sure players follow the rules in a sports game. It is a short way of saying 'referee'.
n. a person who supervises a sporting contest to ensure that the rules are observed and to arbitrate on matters arising from the play. An informal clipping of 'referee'.
The ref blew his whistle to stop the game.
The players argued with the ref after he gave a penalty in the final minute of the match.
While professional leagues use video technology to assist with difficult calls, the ref on the field still maintains the final authority over the flow of the game.
Clippings.
Usage
Commonly used in speech and informal writing; the full form 'referee' is preferred in official reports or formal journalism.