Source : Webster's Revised Unabridged Dictionary (1913)

Lithosphere \Lith"o*sphere\, n. [Litho- + sphere.] (Phys. Geog.)
   (a) The solid earth as distinguished from its fluid
       envelopes, the hydrosphere and atmosphere.
   (b) The outer part of the solid earth, the portion undergoing
       change through the gradual transfer of material by
       volcanic eruption, the circulation of underground water,
       and the process of erosion and deposition. It is,
       therefore, regarded as a third mobile envelope comparable
       with the hydrosphere and atmosphere.

Source : WordNet®

lithosphere
     n : the solid part of the earth consisting of the crust and
         outer mantle [syn: {geosphere}]