Line1  —n. 1 continuous mark made on a surface. 2 similar mark, esp. A furrow or wrinkle. 3 use of lines in art. 4 a straight or curved continuous extent of length without breadth. B track of a moving point. 5 contour or outline (has a slimming line). 6 a curve connecting all points having a specified common property. B (the line) the equator. 7 a limit or boundary.