backline

/B AE1 K L AY0 N/
noun
  1. 1

    Collectively, the players known as backs, whose job it is to create and exploit space.

  2. 2

    The imaginary tactical line across the field that passes through the backs, through their primary line of attack/defence (i.e. excluding any players in a more backward defensive position).

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