What is "level line"

Level \Lev"el\ (l[e^]v"[e^]l), a.

1. Even; flat; having no part higher than another; having, or conforming to, the curvature which belongs to the undisturbed liquid parts of the earth's surface; as, a level field; level ground; the level surface of a pond or lake.

   Ample spaces o'er the smooth And level pavement.
   --Milton.

2. Coinciding or parallel with the plane of the horizon; horizontal; as, the telescope is now level.

3. Even with anything else; of the same height; on the same line or plane; on the same footing; of equal importance; -- followed by with, sometimes by to.

   Young boys and girls Are level now with men; the odds is gone.
   --Shak.

   Everything lies level to our wish.
   --Shak.

4. Straightforward; direct; clear; open.

   A very plain and level account.
   --M. Arnold.

5. Well balanced; even; just; steady; impartial; as, a level head; a level understanding. [Colloq.] `` A level consideration.''
   --Shak.

6. (Phonetics) Of even tone; without rising or falling inflection.
   --H. Sweet.

   Level line (Shipbuilding), the outline of a section which is horizontal crosswise, and parallel with the rabbet of the keel lengthwise.

   Level surface (Physics), an equipotential surface at right angles at every point to the lines of force.