1. What does it mean?
불금 abbreviates 불타는 금요일, burning Friday. It captures the upbeat feeling of being ready to enjoy Friday evening after a week of work or classes, somewhat like an enthusiastic TGIF.
Also written or said as bulgeum
2. The nuance
It does not require drinking, clubbing, or staying out. People can jokingly celebrate 불금 at home, and the weekend feeling depends on their own schedule.
3. Examples
“불금이라 친구들이랑 보드게임 하기로 했어.”
It's Friday night, so we're getting together for board games.
“이번 불금은 집에서 영화 보면서 보낼래.”
I'll spend this Friday night watching a movie at home.
Sources
References support the meaning and usage. Example sentences are written for NoCapWiki.