1A radial plate in an echinoderm; = "radial". Usually in plural Now rare.
2The carpal bone which lies on the radial side at the base of the carpus in the tetrapod forelimb (in humans and other mammals called the scaphoid).
3Any of the rays in a fish's fin; = "radial". Usually in plural.
Mid 19th century; earliest use found in American Naturalist. From post-classical Latin radiale, neuter singular of radialis.