1. What does it mean?
비계 shortens 비공개 계정. It commonly describes an account whose posts are restricted to approved followers rather than openly visible to everyone.
Also written or said as 비공개 계정, bigye
2. The nuance
Private visibility is different from having a small audience or a secondary account. Screenshots can still travel beyond that audience, so 비계 is not a promise of secrecy.
3. Examples
“일상 이야기는 가까운 친구만 있는 비계에 써.”
I write about my daily life on a private account with just close friends.
“비계에 올린 사진은 허락 없이 옮기지 말아 줘.”
Please don't repost photos from my private account without permission.
Sources
References support the meaning and usage. Example sentences are written for NoCapWiki.