also base-line
(~s)
1.
The ~ of a tennis, badminton, or basketball court is one of the lines at each end of the court that mark the limits of play.
Martinez, when she served, usually stayed on the ~.
N-COUNT: usu sing
2.
In baseball, the ~ is the line that a player must not cross when running between bases.
N-COUNT: usu sing
3.
A ~ is a value or starting point on a scale with which other values can be compared.
You’ll need such information to use as a ~ for measuring progress.
N-COUNT: usu sing, oft N for n/-ing