The verb threaten has 3 senses (first 3 from tagged texts)
1. (23) endanger, jeopardize, jeopardise, menace, threaten, imperil, peril -- (pose a threat to; present a danger to; "The pollution is endangering the crops")
2. (21) threaten -- (to utter intentions of injury or punishment against:"He threatened me when I tried to call the police")
3. (10) threaten -- (to be a menacing indication of something:"The clouds threaten rain"; "Danger threatens")