a closed book (to somebody)
成語所屬單字book
a closed book (to somebody) — 慣用語
1. This refers to a subject or person that you know nothing about.
1.慣用語
釋義
一無所知的事物或人
This refers to a subject or person that you know nothing about.
例句
Advanced mathematics is a closed book to me.
Why is her past a closed book to everyone?