The Collaborative International Dictionary of English v.0.48:

Forswear \For*swear"\, v. t. [imp. Forswore; p. p. Forsworn;
   p. pr. & vb. n. Forswearing.] [OE. forsweren, forswerien,
   AS. forswerian; pref. for- + swerian to swear. See For-,
   and Swear, v. i.]
   1. To reject or renounce upon oath; hence, to renounce
      earnestly, determinedly, or with protestations.
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            I . . . do forswear her.              --Shak.
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   2. To deny upon oath.
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            Like innocence, and as serenely bold
            As truth, how loudly he forswears thy gold!
                                                  --Dryden.
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   To forswear one's self, to swear falsely; to perjure one's
      self. "Thou shalt not forswear thyself." --Matt. v. 33.

   Syn: See Perjure.
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WordNet (r) 3.0 (2006):

forswearing
    n 1: the act of renouncing; sacrificing or giving up or
         surrendering (a possession or right or title or privilege
         etc.) [syn: renunciation, forgoing, forswearing]