Wordnet 3.0
ADJECTIVE (1)
1. 
 causing fear or anxiety by threatening great harm; 
- Example: "a dangerous operation"- Example: "a grave situation"- Example: "a grave illness"- Example: "grievous bodily harm"- Example: "a serious wound"- Example: "a serious turn of events"- Example: "a severe case of pneumonia"- Example: "a life-threatening disease"[syn: dangerous, grave, grievous, serious, severe, life-threatening]
WordNet (r) 3.0 (2006):
life-threatening
    adj 1: causing fear or anxiety by threatening great harm; "a
           dangerous operation"; "a grave situation"; "a grave
           illness"; "grievous bodily harm"; "a serious wound"; "a
           serious turn of events"; "a severe case of pneumonia"; "a
           life-threatening disease" [syn: dangerous, grave,
           grievous, serious, severe, life-threatening]