hemisphere

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A half of a sphere bounded by a great circle.
2. n. A half of a symmetrical, approximately spherical object as divided by a plane of symmetry.
3. n. Either half of the celestial sphere as divided by the ecliptic, the celestial equator, or the horizon.
4. n. Either the northern or southern half of the earth as divided by the equator or the eastern or western half as divided by a meridian.
5. n. Anatomy Either of the lateral halves of the cerebrum; a cerebral hemisphere.

Century Dictionary and Cyclopedia

1. n. A half-sphere; one half of a sphere or globe formed by a plane passing through the center. Specifically
2. n. Half of the terrestrial globe; also, half of the celestial globe, or of the surface of the heavens.
3. n. A map or projection of half of the terrestrial or the celestial sphere.
4. n. In anatomy, either of the two large convex and convoluted masses, one on each side, which together with the fornix, corpus callosum, thalamencephalon, mesencephalon, and olfactory lobes make up the cerebrum. See brain, cerebrum, and cerebral.

GNU Webster's 1913

1. n. A half sphere; one half of a sphere or globe, when divided by a plane passing through its center.
2. n. Half of the terrestrial globe, or a projection of the same in a map or picture.
3. n. The people who inhabit a hemisphere.

WordNet 3.0

1. n. either half of the cerebrum
2. n. half of the terrestrial globe
3. n. half of a sphere