The Collaborative International Dictionary of English v.0.48:

Prevention \Pre*ven"tion\, n. [Cf. F. pr['e]vention.]
   1. The act of going, or state of being, before. [Obs.]
      [1913 Webster]

            The greater the distance, the greater the
            prevention.                           --Bacon.
      [1913 Webster]

   2. Anticipation; esp., anticipation of needs or wishes;
      hence, precaution; forethought. [Obs.] --Hammond. Shak.
      [1913 Webster]

   3. The act of preventing or hindering; obstruction of action,
      access, or approach; thwarting. --South.
      [1913 Webster]

            Casca, be sudden, for we fear prevention. --Shak.
      [1913 Webster]

   4. Prejudice; prepossession. [A Gallicism] --Dryden.
      [1913 Webster]

WordNet (r) 3.0 (2006):

prevention
    n 1: the act of preventing; "there was no bar against leaving";
         "money was allocated to study the cause and prevention of
         influenza" [syn: prevention, bar]

Moby Thesaurus II by Grady Ward, 1.0:

126 Moby Thesaurus words for "prevention":
   Eighteenth Amendment, Prohibition Party, Volstead Act, abortion,
   anticipation, arrest, arrestation, arresting, avoidance, avoiding,
   avoiding reaction, balk, balking, ban, banning, bar, barring,
   block, blocking, check, checking, circumvention, contraband,
   control, controlling, curb, curbing, debarment, debarring,
   defense mechanism, delay, delaying, denial, determent, deterrence,
   disallowance, discouragement, dodge, duck, elusion, elusiveness,
   embargo, enjoining, equivocation, escape, estoppel, evasion,
   evasive action, evasiveness, exclusion, foiling, forbearance,
   forbiddance, forbidden fruit, forbidding, foreclosure,
   forestalling, forestallment, frustrating, frustration,
   getting around, halt, halting, hampering, hindering, hindrance,
   impedance, impeding, index, index expurgatorius,
   index librorum prohibitorum, inhibiting, inhibition, injunction,
   intercepting, interception, interdict, interdicting, interdiction,
   interdictum, jink, law, mitigating, mitigation, neutrality, no-no,
   nonintervention, noninvolvement, obstructing, obstruction,
   obviation, preclusion, prohibiting, prohibition,
   prohibitory injunction, proscribing, proscription, refraining,
   refusal, rejection, repression, restraining, restraint,
   restrictive covenants, retardation, ruling out, shunning,
   shunting off, shy, sidestep, sidetracking, slip, slowing, statute,
   stay, stop, stoppage, stopping, sumptuary laws, suppression, taboo,
   the runaround, thwarting, zigzag, zoning, zoning laws



Bouvier's Law Dictionary, Revised 6th Ed (1856):

PREVENTION, civil and French law. The right of a judge to take cognizance of
an action over which he has concurrent jurisdiction with another judge.
     2. In Pennsylvania it has been ruled that a justice of the peace cannot
take cognizance of a cause which has been previously decided by another
justice. 2 Dall. 77; Id. 114.