The Collaborative International Dictionary of English v.0.48:

Contour \Con*tour"\, n. [F. contour, fr. contourner to mark the
   outlines; con- + tourner to turn. See Turn.]
   1. The outline of a figure or body, or the line or lines
      representing such an outline; the line that bounds;
      periphery.
      [1913 Webster]

            Titian's coloring and contours.       --A. Drummond.
      [1913 Webster]

   2. (Mil.) The outline of a horizontal section of the ground,
      or of works of fortification.
      [1913 Webster]

   Contour feathers (Zool.), those feathers that form the
      general covering of a bird.

   Contour of ground (Surv.), the outline of the surface of
      ground with respect to its undulation, etc.

   Contour line (Topographical Suv.), the line in which a
      horizontal plane intersects a portion of ground, or the
      corresponding line in a map or chart.
      [1913 Webster]

WordNet (r) 3.0 (2006):

contour line
    n 1: a line drawn on a map connecting points of equal height
         [syn: contour, contour line]