The Collaborative International Dictionary of English v.0.48:

Preponderate \Pre*pon"der*ate\, v. t. [imp. & p. p.
   Preponderated; p. pr. & vb. n. Preponderating.] [L.
   praeponderatus, p. p. of praeponderare; prae before +
   ponderare to weigh, fr., pondus, ponderis, a weight. See
   Ponder.]
   1. To outweigh; to overpower by weight; to exceed in weight;
      to overbalance.
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            An inconsiderable weight, by distance from the
            center of the balance, will preponderate greater
            magnitudes.                           --Glanvill.
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   2. To overpower by stronger or moral power.
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   3. To cause to prefer; to incline; to decide. [Obs.]
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            The desire to spare Christian blood preponderates
            him for peace.                        --Fuller.
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The Collaborative International Dictionary of English v.0.48:

Preponderate \Pre*pon"der*ate\, v. i.
   To exceed in weight; hence, to incline or descend, as the
   scale of a balance; figuratively, to exceed in influence,
   power, etc.; hence; to incline to one side; as, the
   affirmative side preponderated.
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         That is no just balance in which the heaviest side will
         not preponderate.                        --Bp. Wilkins.
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WordNet (r) 3.0 (2006):

preponderate
    v 1: weigh more heavily; "these considerations outweigh our
         wishes" [syn: preponderate, outweigh, overbalance,
         outbalance]