The Collaborative International Dictionary of English v.0.48:
Ovum \O"vum\ ([=o]"v[u^]m), n.; pl. L. Ova ([=o]"v[.a]), E.
Ovums ([=o]"v[u^]mz). [L., an egg. See Oval.]
1. (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.
Note: The ovum is a typical cell, with a cell wall, cell
substance, nucleus, and nucleolus. In man and the
higher animals the cell wall, a vertically striated
membrane, is called the zona pellucida; the cell
contents, the vitellus; the nucleus, the germinal
vesicle; and the nucleolus, the germinal spot. The
diameter of the ripe ovum in man and the domestic
animals varies between 1-200 and 1-120 of an inch.
2. (Arch.) One of the series of egg-shaped ornaments into
which the ovolo is often carved. --Gwilt.