IPA: /ˈɡruːsəmnəs/
KK: /ˈgruːsəmnəs/
The quality or state of being very unpleasant, shocking, or causing horror.
The gruesomeness of the crime scene left a lasting impression on the investigators.
Gruesomeness → It is formed from "gruesome" (from Middle English *gruesom*, meaning causing horror or disgust) and the suffix "-ness" (meaning the state or quality of). The word "gruesomeness" refers to the quality of being gruesome or causing horror.
Think of something that causes horror or disgust ('gruesome') and remember that 'gruesomeness' refers to the state of being that way.