an activity done in addition to one's main job, especially to earn extra income

a sideline career as a stand-up comic

either of the two lines bounding the longer sides of a football field, basketball court, tennis court, or similar playing area

Gascoigne celebrated his goal by sprinting to the sidelines

a position where one is observing a situation rather than being directly involved in it

the US has chosen to remain on the sidelines

we are not just watching from the sidelines, we are rolling our sleeves up and getting involved

cause (a player) to be unable to play in a team or game

an ankle injury has sidelined him for two weeks

remove from the centre of activity or attention; place in a less influential position

backbench MPs have been sidelined and excluded from decision-making