yolk Syllabification: (yolk)Pronunciation: /yōk/Translate yolk | into French | into German | into Italian | into Spanish Definition of yolk noun the yellow internal part of a bird’s egg, which is surrounded by the white, is rich in protein and fat, and nourishes the developing embryo. Zoology the corresponding part in the ovum or larva of all egg-laying vertebrates and many invertebrates. Derivatives yolked adjective [also in combination] yolkless adjective yolky adjective Origin: Old English geol(o)ca, from geolu 'yellow'yolk in other Oxford dictionaries Definition of yolk in the British & World English dictionary