Source : Webster's Revised Unabridged Dictionary (1913)

Diameter \Di*am"e*ter\, n. [F. diam[`e]tre, L. diametros, fr.
   Gr. ?; dia` through + ? measure. See {Meter}.]
   1. (Geom.)
      (a) Any right line passing through the center of a figure
          or body, as a circle, conic section, sphere, cube,
          etc., and terminated by the opposite boundaries; a
          straight line which bisects a system of parallel
          chords drawn in a curve.
      (b) A diametral plane.

   2. The length of a straight line through the center of an
      object from side to side; width; thickness; as, the
      diameter of a tree or rock.

   Note: In an elongated object the diameter is usually taken at
         right angles to the longer axis.

   3. (Arch.) The distance through the lower part of the shaft
      of a column, used as a standard measure for all parts of
      the order. See {Module}.

   {Conjugate diameters}. See under {Conjugate}.

Source : WordNet®

diameter
     n 1: the length of a straight line passing through the center of
          a circle and connecting two points on the circumference
          [syn: {diam}]
     2: a straight line connecting the center of a circle with two
        points on its perimeter (or the center of a sphere with
        two points on its surface)

Source : Free On-Line Dictionary of Computing

diameter
     
        The diameter of a {graph} is the maximum value of the minimum
        distance between any two nodes.