Hemisphere

n.
  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.
    4. 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    two hemispherical cups forming, when placed together, a cavity from which the air can be withdrawn by an air pump; -- used to illustrate the pressure of the air.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.