prevent in WordNet English dictionary

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"
   prevent  forestall  foreclose  preclude  forbid 
   
2. stop (someone or something) 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"
   prevent  keep