tocsin

1 an object intended to give public notice or warning <the tocsin rang out, warning us of the approaching tornado> Synonyms flag, signalRelated Words red light; knell

2 something that tells of approaching danger or risk <noted that a sudden drop in a student's grades may be a tocsin of a serious personal problem> Synonyms caution, red flag, red light, tip-off, warning, wake-up callRelated Words omen, portent, premonition, presage; notice, notification; buoy, indicator, knell, sign, signal; foretaste, foretoken; announcement, declarationNear Antonyms all clear