The verb prevent has 2 senses (first 2 from tagged texts)
1. (63) prevent, forestall, foreclose, preclude, forbid -- (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")
2. (40) prevent, keep -- (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")