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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Only at Lou’s funeral, after a woman with whom Lou had an affair shows up, does Tom realize that his father’s life contained unknown mysteries.—
The New Yorker,
New Yorker,
6 Apr. 2026 -
From roughly 4,000 miles away, the view could soon offer rare insights into the moon’s enduring mysteries, said Judd Frieling, Artemis II ascent flight director.—
Alexandra Banner,
CNN Money,
6 Apr. 2026
Noun
-
Check out the all new PLAY hub with puzzles, games and more!—
Ralphie Aversa,
USA Today,
2 Apr. 2026
-
There are many puzzles that hint at this.—
Big Think,
Big Think,
19 Mar. 2026
Noun
-
In 2024, the National Institute of Standards and Technology published new codes that can keep secrets safe from both classical and quantum computers.—
Quanta Magazine,
Quanta Magazine,
3 Apr. 2026
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However, everything changes with the arrival of a new neighbor (James Marsden), who threatens to expose Coop’s secrets.—
Liza Esquibias,
PEOPLE,
3 Apr. 2026
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“Closed books.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/closed%20books. Accessed 7 Apr. 2026.
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