To put a barrier before; hence, to shut out; to hinder; to stop; to impede.

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.

keep from happening or arising; have the effect of preventing; "My sense of tact forbids an honest answer"

To prevent or stop.

make impossible, especially beforehand

As in "precludes credit for Anthropology 301." A preclusion indicates you will not receive credit if you take the precluded course later.