/ fɔːˈstɔːl; NAmE fɔːrˈs-/ verb
[ vn ] to prevent sth from happening or sb from doing sth by doing sth first :
Try to anticipate what your child will do and forestall problems.
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WORD ORIGIN
Old English foresteall 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).