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
Relevance
Example Sentences
Recent Examples of Synonyms for closed books
Noun
-
What to read next The four-part series tackles the origins of the universe, the pivotal role of stardust in all living things, and the nature of space-time, among many other cosmic mysteries.—
David Faris,
TheWeek,
13 Apr. 2026 -
Add it to the list of mysteries surrounding the late actress.—
Bailey Bujnosek,
InStyle,
13 Apr. 2026
Noun
-
To find her way out, Miskwa must solve puzzles and navigate different environments while learning Ojibwe words and phrases along the way.—
Joe Van Ryn,
CBS News,
15 Apr. 2026
-
Check out the all new PLAY hub with puzzles, games and more!—
James Powel,
USA Today,
15 Apr. 2026
Noun
-
When secrets are a matter of national security Now consider how much worse that problem becomes if that AI helper works for the CIA, where secrecy is a matter of national security and breaches could endanger lives.—
Erik German,
Fortune,
11 Apr. 2026
-
Its secrets have been passed down through four generations.—
Bill Addison,
Los Angeles Times,
11 Apr. 2026
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Cite this Entry
“Closed books.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/closed%20books. Accessed 19 Apr. 2026.
Copy CitationLove words? Need even more definitions?
Merriam-Webster unabridged
