\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}.