1. What does it mean?
A compact expression built from 혼자 ('alone') and 밥 ('rice' or, more broadly, 'a meal'). 혼밥하다 means to eat by yourself, whether at home, at a restaurant, or during a break.
Also written or said as 혼밥하다
2. The nuance
It describes who you are eating with, not how you feel. A solo meal may be relaxed, practical, or lonely depending on the situation; the word alone does not settle that.
3. Examples
“오늘은 일정이 안 맞아서 점심 혼밥할게.”
Our schedules don't line up today, so I'll have lunch on my own.
“혼밥하기 편한 식당을 찾고 있어.”
I'm looking for a restaurant that's comfortable for eating alone.
Sources
Korean Cultural Center Germany: Korean food culture
References support the meaning and usage. Example sentences are written for NoCapWiki.