grievous in WordNet English dictionary

1. shockingly brutal or cruel
   "murder is an atrocious crime"; "a grievous offense against morality"; "a grievous crime"; "no excess was too monstrous for them to commit"
   atrocious  flagitious  grievous  monstrous 
   
2. 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"
   dangerous  grave  grievous  serious  severe  life-threatening 
   
3. of great gravity or crucial import; requiring serious thought
   "grave responsibilities"; "faced a grave decision in a time of crisis"; "a grievous fault"; "heavy matters of state"; "the weighty matters to be discussed at the peace conference"
   grave  grievous  heavy  weighty 
   
4. causing or marked by grief or anguish
   "a grievous loss"; "a grievous cry"; "her sigh was heartbreaking"; "the heartrending words of Rabin's granddaughter"
   grievous  heartbreaking  heartrending