linesman

/L AY1 N S M AH0 N/
noun
  1. 1

    An assistant referee.

  2. 2

    A male line judge.

  3. 3

    An official whose primary task is to watch the blue line and determine when there has been an offside.

  4. 4

    An official whose primary task is to determine whether there has been a line of scrimmage violation.

  5. 5

    A person employed to work on electrical lines; a lineman.

  6. 6

    A private in the line.

Source: https://en.wiktionary.org/wiki/linesman