WordWeb Online

1. Pose a threat to; present a danger to
   "The pollution is threatening the crops"
   - endanger, jeopardize, jeopardise [Brit], menace, imperil, peril
    
2. To utter intentions of injury or punishment against
   "He threatened me when I tried to call the police"
    
3. To be a menacing indication of something
   "The clouds threaten rain"; "Danger threatens"

Derived forms: threatening, threatens, threatened

Type of: augur, auspicate, be, betoken [archaic], bode, exist, forecast, foreshadow, foretell, omen, portend, predict, prefigure, presage, prognosticate, warn