prevent 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"
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"
an obstruction that stands in the way (and must be removed or surmounted or circumvented)
something immaterial that stands in the way and must be circumvented or surmounted; "lack of imagination is an obstacle to one's advancement"; "the poverty of a district is an obstacle to good education"; "the filibuster was a major obstruction to the success of their plan"