ornithology UK /ˌɔːnɪˈθɒlədʒi/US /ˌɔɹnɪˈθɑlədʒi/ noun1 •The branch of zoology that deals with the scientific study of birds.Gesner says in his Ornithology, that this fact was attested by a great many moderns of his own time, and he even quotes Albert the great, who asserts that he has seen a cock foster chickens. — 1750 formsornithologies