What is the meaning of Sideline?

A line at the side of something.

Something that is additional or extra or that exists around the edges or margins of a main item.

A line for hobbling an animal by connecting the fore and the hind feet of the same side.

A line defining the side boundary of a playing field. Used in Canadian football, field lacrosse and basketball.

The area outside the playing field beyond each sideline.

The outside or perimeter of any activity.

A secondary road, especially a byroad at right angles to a main road.

A side hustle.

To place on the sidelines; to bench or to keep someone out of play.

To remove or keep out of circulation or out of the focus.

Source: wiktionary.org