as in mysteries
something hard to understand or explain
the couple's unorthodox marriage is definitely a closed book to those outside of the relationship
Synonyms & Similar Words
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Example Sentences
Recent Examples of Synonyms for closed books
Noun
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New York — One of the biggest mysteries of the global economy is why the oil market has remained so calm during one of the greatest supply shocks in history.—
Matt Egan,
CNN Money,
9 June 2026 -
Solving the mysteries of Lewis’s art hasn’t been easy.—
Zachary Fine,
New Yorker,
8 June 2026
Noun
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Check out the all new PLAY hub with puzzles, games and more!—
Liza Esquibias,
USA Today,
10 June 2026
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To test that, the final group completed cognitively demanding games such as mazes and shape puzzles called tangrams that contained no academic content.—
Supreet Kaur,
Scientific American,
10 June 2026
Noun
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Critical information including intellectual property, military intelligence, medical records, and government secrets may be in danger.—
Chuck Brooks,
Forbes.com,
13 June 2026
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But when one of them is murdered, private investigator Aubrey Merritt and her assistant Olivia Blunt must unravel decades of secrets and fractured loyalties to uncover the killer.—
Kait Hanson,
Southern Living,
13 June 2026
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“Closed books.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/closed%20books. Accessed 16 Jun. 2026.
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