diameter

n. 1 straight line passing through the centre of a circle or sphere to its edges; length of this. 2 transverse measurement; width, thickness. 3 unit of linear magnifying power. [greek: related to *-meter]

n. 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.