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closed book

noun

Definition of closed book

:something beyond comprehension :enigma

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Examples of closed book in a Sentence

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

First Known Use of closed book

1913

closed book Synonyms

Synonyms
mystery, conundrum, enigma, head-scratcher, mystification, puzzle, puzzlement, riddle, secret
Related Words
brainteaser, case, challenge, knot, matter, perplexity, poser, problem, stumper, trouble

Learn More about closed book

  1. See words that rhyme with closed book Thesaurus: All synonyms and antonyms for closed book

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Examples: closed book in a Sentence