verb

inform (someone) of a possible future danger or problem.

he had been forewarned of a coup plot

warn,prewarn,warn in advance,give advance warning,give fair warning,give notice,advise,apprise,inform,put on one’s guard about,alert about,caution about,tip off about,put wise to,put in the picture about,clue in about,tip someone the wink about,premonish,harbinger,omen,augury,sign,signal,herald,indication,presage,portent,promise,prediction,forecast,premonition,warning,advance warning,prior warning,tip-off,foretoken