diameter

noun

1. Geometry.
   1. a straight line passing through the center of a circle or sphere and meeting the circumference or surface at each end.
   2. a straight line passing from side to side of any figure or body, through its center.
2. the length of such a line.
3. the width of a circular or cylindrical object.

noun

1. 1. a straight line connecting the centre of a geometric figure, esp a circle or sphere, with two points on the perimeter or surface
   2. the length of such a line
2. the thickness of something, esp with circular cross section

n.

late 14c., from Old French diametre, from Latin diametrus, from Greek diametros (gramme) “diagonal of a circle,” from dia- “across, through” (see dia-) + metron “a measure” (see meter (n.2)).

n.

1. A straight line connecting two opposite points on the surface of a spherical or cylindrical body, or at the boundary of an opening or foramen, passing through the center of such body or opening.
2. The distance measured along such a line.

1. A straight line segment that passes through the center of a circle or sphere from one side to the other.
2. The length of such a line segment.

A straight line passing through the center of a figure, especially a circle or sphere, and joining two opposite points on its circumference.