threaten in WordNet English dictionary

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