The Collaborative International Dictionary of English v.0.48:

Forestall \Fore*stall"\, v. t. [imp. & p. p. Forestalled; p.
   pr. & vb. n. Forestalling.] [OE. forstallen to stop, to
   obstruct; to stop (goods) on the way to the market by buying
   them beforehand, from forstal obstruction, AS. forsteal,
   foresteall, prop., a placing one's self before another. See
   Fore, and Stall.]
   1. To take beforehand, or in advance; to anticipate.
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            What need a man forestall his date of grief,
            And run to meet what he would most avoid? --Milton.
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   2. To take possession of, in advance of some one or something
      else, to the exclusion or detriment of the latter; to get
      ahead of; to preoccupy; also, to exclude, hinder, or
      prevent, by prior occupation, or by measures taken in
      advance.
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            An ugly serpent which forestalled their way.
                                                  --Fairfax.
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            But evermore those damsels did forestall
            Their furious encounter.              --Spenser.
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            To be forestalled ere we come to fall. --Shak.
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            Habit is a forestalled and obstinate judge. --Rush.
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   3. To deprive; -- with of. [R.]
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            All the better; may
            This night forestall him of the coming day! --Shak.
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   4. (Eng. Law) To obstruct or stop up, as a way; to stop the
      passage of on highway; to intercept on the road, as goods
      on the way to market.
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   To forestall the market, to buy or contract for merchandise
      or provision on its way to market, with the intention of
      selling it again at a higher price; to dissuade persons
      from bringing their goods or provisions there; or to
      persuade them to enhance the price when there. This was an
      offense at law in England until 1844. --Burrill.

   Syn: To anticipate; monopolize; engross.
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WordNet (r) 3.0 (2006):

forestalling
    n 1: the act of preventing something by anticipating and
         disposing of it effectively [syn: obviation,
         forestalling, preclusion]

Moby Thesaurus II by Grady Ward, 1.0:

86 Moby Thesaurus words for "forestalling":
   agape, agog, all agog, anticipant, anticipating, anticipative,
   anticipatory, arrestation, avoidance, avoiding reaction, awaiting,
   certain, circumvention, confident, debarment, defense mechanism,
   determent, deterrence, deterrent, deterring, discouragement,
   discouraging, dodge, duck, eager, elusion, elusiveness,
   equivocation, escape, estoppel, evasion, evasive action,
   evasiveness, expectant, expecting, forbearance, forbiddance,
   forbidding, forearmed, foreclosure, forestallment, forewarned,
   gaping, getting around, halt, hopeful, in anticipation,
   in expectation, jink, looking for, looking forward to, neutrality,
   nonintervention, noninvolvement, not surprised, obviation,
   optimistic, preclusion, preclusive, prepared, preventative,
   prevention, preventive, prohibition, prohibitive, prophylactic,
   ready, refraining, sanguine, shunning, shunting off, shy, sidestep,
   sidetracking, slip, stay, stop, stoppage, stopping, sure,
   the runaround, unsurprised, waiting, waiting for, watching for,
   zigzag



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

FORESTALLING, crim. law. Every practice or device, by act, conspiracy,
words, or news, to enhance the price of victuals or other provisions. 3
Inst. 196; Bac. Ab. h.t.; 1 Russ. Cr. 169; 4 Bl. Com. 158.
     2. All endeavors whatever to enhance the common price of any
merchandise, and all kinds of practices which have that tendency, whether by
spreading false rumors, or buying things in a market before the accustomed
hour, are offences at common law, and come under the notion of forestalling,
which includes all kind of offences of this nature. Hawk. P. C. b. 1 c. 8 0,
s. 1. Vide 13 Vin. Ab. 430; Dane's Ab. Index, h.t.; 4 Com. Dig. 391 1 East,
Rep. 132.