Definition of: yolk

(yōk, yōlk) noun
1. The yellow portion of an egg.
2. Biol. That portion of the contents or substance of the ovum which is used for the nourishment and formation of the embryo, consisting of fat or oil drops, etc., as distinguished from the albumen or white of an egg. ♦ Collateral adjective: vitelline.
3. A fine yellow soapy exudation in sheep's wool. [OE geol(o)ca, lit., (the) yellow part <geolu yellow]