Definitions of grievous:

• adjective:   causing or marked by grief or anguish

  Example: "A grievous loss"

• adjective:   of great gravity or crucial import; requiring serious thought

  Example: "A grievous fault"

• adjective:   causing fear or anxiety by threatening great harm

  Example: "Grievous bodily harm"

• adjective:   shockingly brutal or cruel

  Example: "A grievous offense against morality"