n. 1 the yellow internal part of an egg that nourishes the young before it hatches. 2 Biol. the corresponding part of any animal ovum. yolk-bag (or -sac) a membrane enclosing the yolk of an egg. yolked adj. (also in comb.). yolkless adj. yolky adj.
[ OE geol(o)ca f. geolu YELLOW ]