egg tooth

noun

1. a calcareous prominence at the tip of the beak or upper jaw of an embryonic bird or reptile, used to break through the eggshell at hatching.

noun

1. (in embryo birds and reptiles) a temporary tooth or (in birds) projection of the beak used for piercing the eggshell

1. A hard, toothlike projection from the beak of embryonic birds, or from the upper jaw of embryonic reptiles, that is used to cut the egg membrane and shell upon hatching and that later falls off.