Side line. 1. (a) A line pert. or attached to the side of a thing. (b) Specif., a line for hobbling an animal by connecting the fore and the hind feet of the same side.

2. (a) A line of goods sold in addition to one's principal articles of trade; a course of business pursued aside from one's regular occupation. (b) A secondary road; esp., a byroad at right angles to a main road. [Canada]

Side line. 1. (a) A line pert. or attached to the side of a thing. (b) Specif., a line for hobbling an animal by connecting the fore and the hind feet of the same side.

2. (a) A line of goods sold in addition to one's principal articles of trade; a course of business pursued aside from one's regular occupation. (b) A secondary road; esp., a byroad at right angles to a main road. [Canada]

• (usually plural) The boundaries of a playing field.
       The coach stood on the sidelines and bellowed commands at the team.
  
• The outside or perimeter of any activity.
       She installed the whole fixture while he simply watched from the sidelines.
  
• To place on the sidelines; to bench or to keep someone out of play.
       The coach sidelined the player until he regained his strength.
  
• To remove or keep out of circulation.
       The illness sidelined him for weeks.