lineumpire
nounUK /ˈlaɪn ʌmˌpaɪə/
US /ˈlaɪn ʌmˌpaɪr/
A line umpire is a person who watches the lines in a game and says if the ball is in or out.
The line umpire called the ball out, so the player lost the point.
OTHER MEANINGS
2. An official in tennis who judges whether a ball lands inside or outside the lines.
The line umpire raised a hand to signal the ball was out.
3. An assistant official in sports like volleyball or badminton who watches boundary lines.
The line umpire watched closely as the shuttlecock landed near the line.
4. A person who helps the main referee by making calls about the sidelines.
The head referee asked the line umpire for help with the close call.