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
To purchase the complete supply of a good, particularly foodstuffs, in order to charge a monopoly price
If you forestall someone, you realize what they are likely to do and prevent them from doing it. Large numbers of police were in the square to forestall any demonstrations. = stop. to prevent something from happening or prevent someone from doing something by doing something first
To prevent, delay or hinder something by taking precautionary or anticipatory measures; to avert