Source : Webster's Revised Unabridged Dictionary (1913)

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.

            What need a man forestall his date of grief, And run
            to meet what he would most avoid?     --Milton.

   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.