Prevented or hindered in advance; blocked before something could happen.
From 'forestall' (Old English 'forestal,' meaning to ambush or intercept). Originally meant literally 'to stand in front of' a seller to prevent trade. Past participle indicates completed action.
Forestalling was literally illegal in Medieval markets—if you bought goods before they reached the market to sell them at higher prices, you were a forestaller and could be punished.
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