The Collaborative International Dictionary of English v.0.48:

Prevent \Pre*vent"\, v. t. [imp. & p. p. Prevented; p. pr. &
   vb. n. Preventing.] [L. praevenire, praeventum; prae before
   + venire to come. See Come.]
   1. To go before; to precede; hence, to go before as a guide;
      to direct. [Obs.]
      [1913 Webster]

            We which are alive and remain unto the coming of the
            Lord shall not prevent them which are asleep. --1
                                                  Thess. iv. 15.
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            We pray thee that thy grace may always prevent and
            follow us.                            --Bk. of
                                                  Common Prayer.
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            Then had I come, preventing Sheba's queen. --Prior.
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   2. To be beforehand with; to anticipate. [Obs.]
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            Their ready guilt preventing thy commands. --Pope.
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   3. To intercept; to hinder; to frustrate; to stop; to thwart.
      "This vile purpose to prevent." --Shak.
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            Perhaps forestalling night prevented them. --Milton.
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The Collaborative International Dictionary of English v.0.48:

Prevent \Pre*vent"\, v. i.
   To come before the usual time. [Obs.]
   [1913 Webster]

         Strawberries . . . will prevent and come early.
                                                  --Bacon.
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WordNet (r) 3.0 (2006):

prevent
    v 1: keep from happening or arising; make impossible; "My sense
         of tact forbids an honest answer"; "Your role in the
         projects precludes your involvement in the competitive
         project" [syn: prevent, forestall, foreclose,
         preclude, forbid]
    2: stop (someone or something) from doing something or being in
       a certain state; "We must prevent the cancer from spreading";
       "His snoring kept me from falling asleep"; "Keep the child
       from eating the marbles" [syn: prevent, keep] [ant:
       allow, let, permit]