n. The inner one of the two bones of the forearm, between the elbow and the wrist, the other being the radius; the bone which makes a strict hinge-joint at the elbow with the humerus, and about which the radius revolves in pronation and supination, when the ulna reaches to the wrist and these movements are practicable.n. In entomology, the stigmatic or marginal vein of the fore wing.n. A unit of length; a cubit; an ell.n. In ichthyology, the hypereoracoid.