| a broad membrane bone of the skull, forming the forehead and the upper portion of each orbit. |

| frontal bone n. A cranial bone consisting of a vertical portion corresponding to the forehead and a horizontal portion that forms the roofs of the orbital and nasal cavities. |
frontal bone n.
A cranial bone consisting of a vertical portion corresponding to the forehead and a horizontal portion that forms the roofs of the orbital and nasal cavities.