any of five great divisions of the earth's surface with respect to latitude and temperature. a portion of the surface of a sphere included between two parallel planes. GIRDLE, BELT. an encircling anatomical structure. a subdivision of a biogeographic region that supports a similar fauna and flora throughout its extent. such a zone dominated by a particular life form. a distinctive belt, layer, or series of layers of earth materials (such as rock). a region or area set off as distinct from surrounding or adjoining parts. one of the sections of an area or territory created for a particular purpose: such as a zoned section of a city - any of the eight concentric bands of territory centered on a given postal shipment point designated as a distance bracket for U.S. parcel post to which mail is charged at a single rate - a distance within which the same fare is charged by a common carrier - an area on a field of play - a stretch of roadway or a space in which certain traffic regulations are in force. ZONE DEFENSE. a temporary state of heightened concentration experienced by a performing athlete that enables peak performance. to surround with a zone: ENCIRCLE. to arrange in or mark off into zones. ZONAL sense 1. of, relating to, or occurring in a zone defense.