tip–off

something that tells of approaching danger or risk the retreat of the island's wildlife to higher ground was a tip-off that a tsunami was about to strike Synonyms caution, red flag, red light, tip-off, tocsin, wake-up callRelated Words omen, portent, premonition, presage; notice, notification; buoy, indicator, knell, sign, signal; foretaste, foretoken; announcement, declarationNear Antonyms all clear