Master of ceremonies.
A rapper.
To act as the master of ceremonies (for).
To rap as part of a hip-hop performance.
The official who presides over a curling game.
One of the two white-coated officials who preside over a cricket match.
The official who presides over a tennis match sat on a high chair.
One of the officials who preside over a baseball game.
A match official on the ground deciding and enforcing the rules during play. As of 2007 the Australian Football League uses three; in the past there were two or just one. The other officials, the goal umpires and boundary umpires, are usually referred to by those phrases.
The official who stands behind the line on the defensive side or next to the referee on the offensive side.
A person who arbitrates between contending parties.
To act as an umpire in a game.
To decide as an umpire.