1. What does it mean?
뇌절 describes not knowing when to stop: repeating the same joke too often, stretching a running bit, or continuing something after the audience has had enough.
Also written or said as noejeol
2. The nuance
It is not a literal claim that someone's brain has stopped. The boundary is subjective, so what one group enjoys as a running joke can feel like 뇌절 to another.
3. Examples
“한 번은 웃겼는데 열 번 반복하니 뇌절이야.”
It was funny once, but repeating it ten times is overdoing it.
“소개 멘트는 여기까지 하고 뇌절하지 않을게.”
I'll end the introduction here instead of dragging the bit out.
Sources
References support the meaning and usage. Example sentences are written for NoCapWiki.