sideline

noun

1. A line at the side of something.

   “Like most other fishes, the dragonet varies slightly in colour in different individuals, and at different seasons of the year. Mr. Pennant describes the pupils of the eyes to be of a rich sapphirine blue; the irides fine fiery carbuncle; the pectoral fins light brown; the side-line straight; the colours of the fish yellow, blue, and white, making a beautiful appearance when fresh taken.”

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

   “She started the business as a sideline to her regular work and it ended up becoming the greater source of income.”

   “Soup need not be just a sideline to a meal; if you like, it can be the main course.”

   “I often do electronic repairs as a sideline.”

3. A line for hobbling an animal by connecting the fore and the hind feet of the same side.
4. A line defining the side boundary of a playing field. Used in Canadian football, field lacrosse and basketball.
5. (plural-normally)The area outside the playing field beyond each sideline.

   “The coach stood on the sidelines and bellowed commands at the team.”

6. (figuratively)The outside or perimeter of any activity.

   “to relegate to the sidelines”

   “She installed the whole fixture while he simply watched from the sidelines.”

   “Conservative Catholics, Relegated to Sidelines, Denounce Papal Gathering [title]”

7. (Canada)A secondary road, especially a byroad at right angles to a main road.
8. (Philippines)A side hustle.

verb

1. (transitive)To place on the sidelines; to bench or to keep someone out of play.

   “The coach sidelined the player until he regained his strength.”

   “Gomez got his chance with Gary Cahill sidelined and took it superbly with an assured performance as part of a three-man defence Southgate now looks certain to use at the World Cup.”

2. (figuratively, transitive)To remove or keep out of circulation or out of the focus.

   “The illness sidelined him for weeks.”

   “Subplots that might have been fun to explore were relegated or eventually sidelined altogether in the case of characters like Gendry, who disappeared for years and finally resurfaces as a blacksmith in King’s Landing, literally waiting for the call to his hero’s journey.”

   “During 1971-72, spare Type 4s on other regions enabled the whole class to be sidelined, with Class 43s going first.”

   “Prigozhin’s exclusion from Ukraine would sideline one of Russia’s most recognisable war figures.”

   “At National Review, he [William Buckley] got rid of the Birchites—a conspirational fringe claiming Eisenhower for a communist—tamed the libertarians, dropped (eventually) the magazine's white racism and sidelined its antisemites.”