1. What does it mean?
혼술 combines 혼자, alone, with 술, alcohol. It describes drinking without companions, whether at home or elsewhere, rather than a particular beverage or amount.
Also written or said as honsul
2. The nuance
The word alone does not indicate why someone is drinking or how much. It is not synonymous with loneliness, and it should not be used to pressure someone to drink.
3. Examples
“혼술 대신 오늘은 차를 마시기로 했어.”
Instead of drinking alone, I decided to have tea today.
“그 장면은 식탁에서 혼술하는 모습을 보여 줘.”
The scene shows someone having a drink alone at the dining table.
Sources
References support the meaning and usage. Example sentences are written for NoCapWiki.