Sidelines meaning : 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. Usually in the plural: 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. 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.