Sideline

Sideline

n.
  1. A line pertaining or attached to the side of a thing.
  2. A line of goods sold in addition to one's principal articles of trade; a course of business pursued aside from one's regular occupation.
  3. A secondary road; esp., a byroad at right angles to a main road. [Canada]
  4. Either of two marked lines which delimit the side boundaries of a playing field, as in football or soccer. (Sports)
  5. The areas in a sports arena just beyond the sidelines{4}, where coaches and alternative players sit or stand. (Sports) [plural]

Phrases & Compounds
on the sidelines
not actively involved in an activity, such as a sporting event, but available for use when needed; in reserve; as, the coach kept him on the sidelines for a week.

Sideline

v. t.
  1. To render unable to participate in an activity, such as a sporting event; as, the pitcher was sidelined by a groin injury.