The Collaborative International Dictionary of English v.0.48:

eggshell \egg"shell`\, n.
   1. The shell or exterior covering of an egg. Also used
      figuratively for anything resembling an eggshell.
      [1913 Webster]

   2. (Zo["o]l.) A smooth, white, marine, gastropod shell of the
      genus Ovulum, resembling an egg in form.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

eggshell \egg"shell`\, a.
   1. of a pale, yellowish-white color; as, an eggshell ceiling
      and light green walls.
      [1913 Webster +PJC]

   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.
      [PJC]

WordNet (r) 3.0 (2006):

eggshell
    n 1: the exterior covering of a bird's egg [syn: shell,
         eggshell]

Moby Thesaurus II by Grady Ward, 1.0:

68 Moby Thesaurus words for "eggshell":
   alabaster, alabastrine, albescent, albumen, bubble, caviar, china,
   cream, creamy, delicate, dun-white, egg, egg white, fair,
   fish eggs, flat, glair, glass, glass house, glaucescent, glaucous,
   gloss, gray-white, house of cards, ice, iridescent, ivory,
   ivory-white, light, lint-white, matchwood, mellow, mother-of-pearl,
   nacreous, off-white, old paper, opalescent, ovule, pale, parchment,
   pastel, patinaed, pearl, pearly, pearly-white, piecrust, quiet,
   roe, sad, semigloss, simple, sober, soft, soft-colored, soft-hued,
   softened, somber, spawn, subdued, subtle, sweet, tender, vitellus,
   white, whitish, whity, yellow, yolk