1. What does it mean?
Short for 스스로 불러온 재앙, literally a disaster brought on by oneself. It is used when an avoidable decision comes back to make life harder, such as staying up too late before an early start.
2. The nuance
Often self-deprecating or humorous. Calling someone else's serious misfortune 스불재 can sound callous, so the context matters.
3. Examples
“밤새 영상 보다가 늦잠 잤어. 완전 스불재.”
I stayed up watching videos and overslept. Totally my own doing.
“일정을 전부 같은 날 잡은 건 스불재지.”
Putting every appointment on the same day was a disaster of my own making.
Sources
Korea Housing Finance Corporation: Korean slang guide
References support the meaning and usage. Example sentences are written for NoCapWiki.