IPA: //ˈɡhæstlinəs//
KK: /ˈɡæstlɪnəs/
The quality or state of being very shocking or frightening; something that causes horror or disgust.
The ghastliness of the scene left everyone speechless.
Ghastliness → It is formed from "ghast" (from Old English "gast", meaning ghost or spirit) and "-liness" (meaning the quality of). The word "ghastliness" refers to the quality of being ghostly or terrifying, evoking horror or dread.
Think of the word 'ghost' ('ghast') to remember that 'ghastliness' means the quality of being terrifying or eerie, like a ghost.