Yolk

n.	1.
	1.	The yellow part of an egg; the vitellus.
	2.	(Zool.) An oily secretion which naturally covers the wool of sheep. Yolk cord (Zool.) a slender cord or duct which connects the yolk glands with the egg chambers in certain insects, as in the aphids. Yolk gland (Zool.) a special organ which secretes the yolk of the eggs in many turbellarians, and in some other invertebrates. See Illust. of Hermaphrodite in Appendix. Yolk sack (Anat.) the umbilical vesicle. See under Unbilical.

Noun

1.

yolk - nutritive material of an ovum stored for the nutrition of an embryo (especially the yellow mass of a bird or reptile egg) Synonyms: vitellus

egg, food, nutrient, vitellus