IPA: /ˈɡruːsəm/
KK: /ˈgruːsəm/
Causing a strong feeling of shock or disgust, often because of something violent or horrifying.
The movie was so gruesome that many people left the theater feeling sick.
Gruesome is formed from "grue" (from Old French *grue*, meaning to shudder or tremble) and the suffix "-some" (meaning characterized by or causing). The word describes something that causes shuddering or horror, often due to its shocking or disturbing nature.
Think of something that makes you 'shudder' ('grue') and is 'characterized by' horror ('-some'). This helps you remember that 'gruesome' refers to something that causes a feeling of horror.