[yolk] also yoke n [ME yolke, fr. OE geoloca, fr. geolu yellow--more at yellow] (bef. 12c) 1 a: the yellow spheroidal mass of stored food that forms the inner portion of the egg of a bird or reptile and is surrounded by the white--see egg illustration b archaic: the whole contents of an ovum consisting of a protoplasmic formative portion and an inert nutritive portion c: material stored in an ovum that supplies food to the developing embryo and consists chiefly of proteins, lecithin, and cholesterol
2. [akin to MD ieke yolk (of wool), OE eowu ewe]: oily material in unprocessed sheep wool consisting of wool fat, suint, and debris -- yolked adj -- yolky adj