ovum

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The mature female gamete of an animal; an egg.

from The Century Dictionary.

• noun An egg, in a broad biological sense; the proper product of an ovary; the female germ or seed, which when fertilized by the male sperm, and sometimes without such fecundation, is capable of developing into an individual like the parent.
• noun [capitalized] In conchology, same as Ovulum.
• noun [capitalized] In ichthyology, a genus of fishes.
• noun In architecture, an ornament in the shape of an egg.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Biol.) A more or less spherical and transparent cell, which by a process of multiplication and growth develops into a mass of cells, constituting a new individual like the parent; an egg, spore, germ, or germ cell. See Illust. of mycropyle.
• noun (Arch.) One of the series of egg-shaped ornaments into which the ovolo is often carved.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun cytology The female gamete in animals; the egg cell.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the female reproductive cell; the female gamete