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®

law of gravitation
     n : (physics) the law that states any two bodies attract each
         other with a force that is directly proportional to the
         product of their masses and inversely proportional to the
         square of the distance between them [syn: {Newton's law
         of gravitation}]