closed book
US /kloʊzd bʊk/
UK /kləʊzd bʊk/
慣用句
閉じた本, 未知の事柄
a subject or person about which one knows nothing or very little
例:
•
Quantum physics is a closed book to me.
量子物理学は私にとって閉じた本だ。
•
His past is a closed book; he never talks about it.
彼の過去は閉じた本だ。彼は決してそれについて話さない。