1. (noun) the back line bounding each end of a tennis or handball court; when serving the server must not step over this line

• service line

1. (noun) an imaginary line or standard by which things are measured or compared

• criterion
• measure
• standard
• touchstone

2. (noun) the back line bounding each end of a tennis or handball court; when serving the server must not step over this line

• line

3. (noun) the lines a baseball player must follow while running the bases

• line