| any of the several fat-soluble, antirachitic vitamins D1, D2, D3, occurring in milk and fish-liver oils, esp. cod and halibut, or obtained by irradiating provitamin D with ultraviolet light, essential for the formation of normal bones and teeth. |

| vitamin D n. A fat-soluble vitamin occurring in several forms, especially vitamin D2 or vitamin D3, required for normal growth of teeth and bones, and produced in general by ultraviolet irradiation of sterols found in milk, fish, and eggs. |
vitamin D n.
A fat-soluble vitamin occurring in several forms, especially vitamin D2 or vitamin D3, required for normal growth of teeth and bones, and produced in general by ultraviolet irradiation of sterols found in milk, fish, and eggs.