medicalHBH the inner bone of your lower arm, on the side opposite to your thumb 尺骨 →5see picture at 见图skeleton
Examples from the Corpus
ulna• Right arm, compound spiral fractures or radius and ulna.• Also in a remarkable state of preservation is a flute made h-am the ulna at Vulture.• A shinbone was broken, twisted - as was the ulna in one arm, and several ribs.