to exclude, hinder, or prevent (somebody or something) by taking measures or action in advance
to get ahead of or anticipate (somebody or something)
to buy up (goods) in order to create a short supply and thus raise prices, or to affect (a market) in this way
forestaller noun
forestalment noun
[Middle English forstallen from Old English foresteall act of waylaying, from fore- + steall position, stall]