The Collaborative International Dictionary of English v.0.48:

Thereby \There*by"\, adv.
   1. By that; by that means; in consequence of that.
      [1913 Webster]

            Acquaint now thyself with him, and be at peace;
            thereby good shall come unto thee.    --Job xxii.
                                                  21.
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   2. Annexed to that. "Thereby hangs a tale." --Shak.
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   3. Thereabout; -- said of place, number, etc. --Chaucer.
      [1913 Webster]

WordNet (r) 3.0 (2006):

thereby
    adv 1: by that means or because of that; "He knocked over the
           red wine, thereby ruining the table cloth"

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "thereby":
   by, by dint of, by means of, by use of, by virtue of, by way of,
   hereby, herewith, in virtue of, on, per, thanks to, therefrom,
   therewith, through, upon, whereby, wherewith, wherewithal, with