Source : Webster's Revised Unabridged Dictionary (1913)

Preclude \Pre*clude"\, v. t. [imp. & p. p. {Precluded}; p. pr. &
   vb. n. {Precluding}.] [L. praecludere, praeclusum; prae
   before + claudere to shut. See {Close}, v.]
   1. To put a barrier before; hence, to shut out; to hinder; to
      stop; to impede.

            The valves preclude the blood from entering the
            veins.                                --E. Darwin.

   2. To shut out by anticipative action; to prevent or hinder
      by necessary consequence or implication; to deter action
      of, access to, employment of, etc.; to render ineffectual;
      to obviate by anticipation.

            This much will obviate and preclude the objections.
                                                  --Bentley.

Source : WordNet®

preclude
     v 1: keep from happening or arising; have the effect of
          preventing; "My sense of tact forbids an honest answer"
          [syn: {prevent}, {forestall}, {foreclose}, {forbid}]
     2: make impossible, especially beforehand [syn: {rule out}, {close
        out}]