a declaration of an intention or determination to inflict punishment, injury, etc., in retaliation for, or conditionally upon, some action or course; menace

He confessed under the threat of imprisonment.

an indication or warning of probable trouble

The threat of a storm was in the air.

a person or thing that threatens.

Archaic . to threaten.

noun

blackmail , bluff , commination , fix , foreboding , foreshadowing , fulmination , hazard , impendence , intimidation , menace , omen , peril , portent , presage , risk , thunder , writing on the wall * , forewarning , thundercloud , sword of damocles , anathema , caveat , coercion , comminution , constraint , danger , denunciation , duress , jeopardy , minacity , saber rattling , threatening , ultimatum , warning