**Noun**diameter has 2 senses

- diameter, diam - the length of a straight line passing through the center of a circle and connecting two points on the circumference

--_{1}is a kind of length

--_{1}has parts: radius, r

--_{1}has particulars: bore, gauge, caliber, calibre; windage - diameter - 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)

--_{2}is a kind of straight line