From Longman Dictionary of Contemporary Englishdiameterdi‧am‧e‧ter /daɪˈæmɪtə $ -ər/ ●●○ noun [countable] HMHMa straight line from one side of a circle to the other side, passing through the centre of the circle, or the length of this line3 inches/1 metre etc in diameter Draw a circle six centimetres in diameter.diameter of The diameter of the Earth is about 13,000 km.Examples from the Corpus

diameter• The arms are long and thin, greater than seven times the disk diameter.• When a disc is rolled about a disc of equal diameter, the roller makes two revolutions about its own centre.• In addition, the procedure usually takes longer and an endoscope of a greater diameter is used when biliary stenting is performed.• The belt, however, consists of perhaps forty thousand bodies larger than a kilometer in diameter.• This originally had two large diameter undershot wheels, both of iron construction with timber floats.• He then proceeded to draw a circle of diameter I metre on a flat piece of ground.• For every pebble several possible diameters may be recognized along the three principal axes of the pebble.