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closed book

noun

Definition of closed book 

: something beyond comprehension : enigma

Examples of closed book in a Sentence

the couple's unorthodox marriage is definitely a closed book to those outside of the relationship

First Known Use of closed book

1913, in the meaning defined above

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Dictionary Entries near closed book

closed account

closed banknote

closed bolt

closed book

closed-captioned

closed-captioning

closed-cell

Statistics for closed book

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Time Traveler for closed book

The first known use of closed book was in 1913

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