closed book

See also: closed-book

English

Pronunciation

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Noun

closed book (plural closed books)

1. (idiomatic) A person or thing that cannot be easily understood; someone or something incomprehensible or puzzling.
   • 1906, Mary Cholmondeley, Prisoners:

     Her courteous, sedate, inexorable husband, whose will she could not bend, whom she could not cajole, whose mind was a closed book to her — a book which had lain by her hand for three years, which she had never had the curiosity to open!

   • 1962 April, R. K. Evans, “The Acceptance Testing of Diesel Locomotives”, in Modern Railways, page 266:

     Like the activities of British Railways Research Department, developing, testing and modifying diesel locomotives before their acceptance for service is another behind-the-scenes activity which is a closed book to most passengers and to many railwaymen.

Antonyms

• open book

See also

• enigma
• mystery
• secret