ra·di·al [rey-dee-uhl] adjective 1.arranged like radii or rays. 2.having spokes, bars, lines, etc., arranged like radii, as a machine. 3.made in the direction of a radius; going from the center outward or from the circumference inward along a radius: a radial cut. 4.Zoology . pertaining to structures that radiate from a central point, as the arms of a starfish. 5.of, like, or pertaining to a radius or a ray.