\Pri"mum mob"i*le\ [L., first cause of motion.]
(Astron.)
In the Ptolemaic system, the outermost of the revolving
concentric spheres constituting the universe, the motion of
which was supposed to carry with it all the inclosed spheres
with their planets in a daily revolution from east to west.
See {Crystalline heavens}, under {Crystalline}.

      The motions of the greatest persons in a government
      ought to be, as the motions of the planets, under
      primum mobile.                           --Bacon.