Source : Webster's Revised Unabridged Dictionary (1913)

Gravitation \Grav"i*ta"tion\, n. [Cf. F. gravitation. See
   Gravity.]
   1. The act of gravitating.

   2. (Pysics) That species of attraction or force by which all
      bodies or particles of matter in the universe tend toward
      each other; called also {attraction of gravitation},
      {universal gravitation}, and {universal gravity}. See
      {Attraction}, and {Weight.}

   {Law of gravitation}, that law in accordance with which
      gravitation acts, namely, that every two bodies or
      portions of matter in the universe attract each other with
      a force proportional directly to the quantity of matter
      they contain, and inversely to the squares of their
      distances.

Source : WordNet®

gravitation
     n 1: (physics) the force of attraction between all masses in the
          universe; especially the attraction of the earth's mass
          for bodies near its surface; "the more remote the body
          the less the gravity"; "the gravitation between two
          bodies is proportional to the product of their masses
          and inversely proportional to the square of the distance
          between them"; "gravitation cannot be held responsible
          for people falling in love"--Albert Einstein [syn: {gravity},
           {gravitational attraction}, {gravitational force}]
     2: movement downward resulting from gravitational attraction;
        "irrigation by gravitation rather than by pumps" [ant: {levitation}]
     3: a figurative movement toward some attraction; "the
        gravitation of the middle class to the suburbs"