service line
noun
1- (in tennis, badminton, and other sports) a line on a court marking the limit of the area into which the ball must be served（网球、羽毛球等运动的）发球线。
1.1
- (especially in handball and paddleball) a line on a court marking the boundary of the area in which the server must be standing when serving（尤指手球、板手球运动的）发球线。