The Collaborative International Dictionary of English v.0.48:

Gravitate \Grav"i*tate\, v. i. [imp. & p. p. Gravitated; p.
   pr. & vb. n. Gravitating.] [Cf. F. graviter. See
   Gravity.]
   To obey the law of gravitation; to exert a force or pressure,
   or tend to move, under the influence of gravitation; to tend
   in any direction or toward any object.
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         Why does this apple fall to the ground? Because all
         bodies gravitate toward each other.      --Sir W.
                                                  Hamilton.
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         Politicians who naturally gravitate towards the
         stronger party.                          --Macaulay.
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