linereferee
nounUK /ˈlaɪn ˌrɛfəˈriː/
US /ˈlaɪn ˌrɛfəˈriː/
A line referee is a person who watches a line in a game to say if the ball or player is in or out.
The line referee raised the flag when the ball rolled past the line.
OTHER MEANINGS
2. An official who helps the main referee by watching a boundary line during a match.
The line referee told the referee the player had stepped out of bounds.
3. A person who checks whether a ball crossed a line before a point is given.
The line referee signaled that the ball was in, so the point counted.
4. An assistant on the sideline who reports line calls to the head referee.
The line referee waved the flag to show the ball went out of play.