closed book
US /kloʊzd bʊk/
UK /kləʊzd bʊk/
成語
天書, 不為人知的事
a subject or person about which one knows nothing or very little
範例:
•
Quantum physics is a closed book to me.
量子物理學對我來說是本天書。
•
His past is a closed book; he never talks about it.
他的過去是本天書；他從不談論它。