Webster's Revised Unabridged Dictionary · 1913

eggshell

eggshell , noun

1.
The shell or exterior covering of an egg. Also used figuratively for anything resembling an eggshell.
2.
(Zoology) A smooth, white, marine, gastropod shell of the genus Ovulum, resembling an egg in form.

eggshell , adjective

1.
of a pale, yellowish-white color; as, an eggshell ceiling and light green walls.
2.
(Architecture) having a smooth but not glossy texture like that of a hen's egg; as, a latex paint giving an eggshell finish. Also referred to as matte glaze or non-lustrous glaze.