From The Collaborative International Dictionary of English v.0.48 [gcide]:
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.
[1913 Webster]
The valves preclude the blood from entering the
veins. --E. Darwin.
[1913 Webster]
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.
[1913 Webster]
This much will obviate and preclude the objections.
--Bentley.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
preclude
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: make impossible, especially beforehand [syn: preclude,
rule out, close out]