D defs.my
Entry 1 sense Webster, 1913

Semidiameter

· Sem·i·di·am·e·ter · IPA
01 n. Half of a diameter; a right line, or the length of a right line, drawn from the center of a circle, a sphere, or other curved figure, to it…
  1. 1.
    Half of a diameter; a right line, or the length of a right line, drawn from the center of a circle, a sphere, or other curved figure, to its circumference or periphery; a radius.(Math.)