Definition of: sideline

(sīd′līn′) noun
1. An auxiliary line of goods sold by a store or a commercial traveler.
2. Any additional or secondary work differing from one's main job.
3. A track or road, especially of a railroad, branching off from the main line.
4. A line used to hobble a horse by connecting the fore and hind feet of the same side: also side′–hob′ble (-hob′əl).
5. One of the lines bounding the two sides of a football field, tennis court, or the like; also, the area just outside these lines: often in the plural.
6. The point of view of an outsider or non–participant.