prevent or obstruct (an anticipated event or action) by taking advance action:they will present their resignations to forestall a vote of no confidence
act in advance of (someone) in order to prevent them from doing something:he would have spoken but David forestalled him
historical buy up (goods) in order to profit by an enhanced price.
Old Englishforesteall 'an ambush' (see fore- and stall). As a verb the earliest sense (Middle English) was 'intercept and buy up goods before they reach the market, so as to raise the price' (formerly an offence)
forestall in other Oxford dictionaries
Definition of forestall in the US English dictionary