1N-COUNT [usually singular](网球场、羽毛球场、篮球场等的)底线 The baseline of a tennis, badminton, or basketball court is one of the lines at each end of the court that mark the limits of play. (网球场、羽毛球场、篮球场等的)底线
Martinez, when she served, usually stayed on the baseline.
马丁内兹发球的时候通常站在底线处。
2N-COUNT [usually singular](棒球场的)垒线 In baseball, the baseline is the line that a player must not cross when running between bases. (棒球场的)垒线
3N-COUNT [usually singular]基线;基准 A baseline is a value or starting point on a scale with which other values can be compared. 基线;基准
You'll need such information to use as a baseline for measuring progress. [+ for]