Closed Book, a

Meaning of Idiom ‘A Closed Book’

closed book is someone or something about which you know nothing or which you do not understand; a secret or mystery; a subject that someone does not want to talk about or be asked about. 1Ayto, John. Oxford Dictionary of English Idioms. Oxford: Oxford U, 2010.,2Kirkpatrick, Elizabeth M. The Wordsworth Dictionary of Idioms. Ware: Wordsworth, 1995.,3Ammer, Christine. American Heritage Dictionary of Idioms. Boston: Houghton Mifflin Harcourt, 2013.,4Jarvie, Gordon. Bloomsbury Dictionary of Idioms. London: Bloomsbury, 2009.

See the antonym an open book.

Examples Of Use

“Quantum physics can be a closed book even to those who study it.”

“Nobody really knows Michelle very well. She’s a closed book.”

“For years, the mysterious past of the island was a closed book.”

“Listen, we can talk about anything but my divorce. That is a closed book.”

A closed book idiom meaning

Origin

Used since the early 1900’s, the idiom alludes to being unable to access the information in a book because the book is closed.

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Sources   [ + ]

1. Ayto, John. Oxford Dictionary of English Idioms. Oxford: Oxford U, 2010.
2. Kirkpatrick, Elizabeth M. The Wordsworth Dictionary of Idioms. Ware: Wordsworth, 1995.
3. Ammer, Christine. American Heritage Dictionary of Idioms. Boston: Houghton Mifflin Harcourt, 2013.
4. Jarvie, Gordon. Bloomsbury Dictionary of Idioms. London: Bloomsbury, 2009.