Source : Webster's Revised Unabridged Dictionary (1913)

Hemisphere \Hem"i*sphere\, n. [L. hemisphaerium, Gr. ?; ? half =
   ? sphere: cf. F. h['e]misph[`e]re. See {Hemi-}, and
   {Sphere}.]
   1. A half sphere; one half of a sphere or globe, when divided
      by a plane passing through its center.

   2. Half of the terrestrial globe, or a projection of the same
      in a map or picture.

   3. The people who inhabit a hemisphere.

            He died . . . mourned by a hemisphere. --J. P.
                                                  Peters.

   {Cerebral hemispheres}. (Anat.) See {Brain}.

   {Magdeburg hemispheres} (Physics), two hemispherical cups
      forming, when placed together, a cavity from which the air
      can be withdrawn by an air pump; -- used to illustrate the
      pressure of the air. So called because invented by Otto
      von Guericke at Magdeburg.

Source : WordNet®

hemisphere
     n 1: half of the terrestrial globe
     2: half of a sphere
     3: either half of the cerebrum [syn: {cerebral hemisphere}]