a closed book


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a closed book

Someone or something that is difficult to know or understand. She's such a private person that I don't actually know very much about her. I guess I married a closed book. I'm a scientist through and through, so art has always been a closed book to me.
See also: book, closed
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

closed book, a

A secret, mystery, or puzzle, as in I can't figure her out; she's a closed book to me. This term alludes to information one can't obtain or comprehend (because the book is closed). [Early 1900s]
See also: closed
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

a closed book

BRITISH
If something or someone is a closed book to you, you know or understand very little about them. Economics were a closed book to him. He is such a closed book, that guy. Compare with an open book.
See also: book, closed
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012

a closed book

a thing of which you have no knowledge or understanding.
1944 Frank Clune The Red Heart The desert is an open book to the man of the Vast Open Spaces, but to the schoolmaster it was a closed book.
See also: book, closed
Farlex Partner Idioms Dictionary © Farlex 2017

a closed ˈbook (to somebody)

a person or a subject that you know nothing about: I’m afraid geophysics is rather a closed book to me.Please let’s not talk about her former life, that’s all a closed book now.
See also: book, closed
Farlex Partner Idioms Dictionary © Farlex 2017
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