‖n.; pl. Zonae [ L., a girdle. See Zone. ] A zone or band; a layer. [ 1913 Webster ]

Zona pellucida. [ NL. ] (Biol.) (a) The outer transparent layer, or envelope, of the ovum. It is a more or less elastic membrane with radiating striae, and corresponds to the cell wall of an ordinary cell. See Ovum, and Illust. of Microscope. (b) The zona radiata. --
Zona radiata [ NL. ] (Biol.), a radiately striated membrane situated next the yolk of an ovum, or separated from it by a very delicate membrane only. [ 1913 Webster ]

a. [ L. zonalis. ] Of or pertaining to a zone; having the form of a zone or zones. [ 1913 Webster ]

Zonal equation (Crystallog.), the mathematical relation which belongs to all the planes of a zone, and expresses their common position with reference to the axes. --
Zonal structure (Crystallog.), a structure characterized by the arrangements of color, inclusions, etc., of a crystal in parallel or concentric layers, which usually follow the outline of the crystal, and mark the changes that have taken place during its growth. --
Zonal symmetry. (Biol.) See the Note under Symmetry. [ 1913 Webster ]

n. [ Mod. Gr. &unr_; a girdle, fr. Gr. &unr_;, dim. of &unr_; a girdle. See Zone. ] A belt or girdle which the Christians and Jews of the Levant were obliged to wear to distinguish them from Mohammedans. [ Written also zonnar. ] [ 1913 Webster ]

‖n. pl. [ NL. ] (Zool.) A division of Mammalia in which the placenta is zonelike. [ 1913 Webster ]

a. (Bot.) Divided by parallel planes; as, zonate tetraspores, found in certain red algae. [ 1913 Webster ]