Closed book and Riddle

Closed book

Closed book noun - Something hard to understand or explain.
Usage example: the couple's unorthodox marriage is definitely a closed book to those outside of the relationship
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Synonyms for Closed book

Riddle is a synonym for closed book in puzzle topic. In some cases you can use "Riddle" instead a noun phrase "Closed book", when it comes to topics like mystery.

Riddle

Riddle noun - Something hard to understand or explain.
Usage example: his motives for starting an argument with the coach were a complete riddle
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Synonyms for Riddle

Closed book is a synonym for riddle in brain-teaser topic. You can use "Closed book" instead a noun "Riddle".

Nearby Words: riddled, riddling
Cite this Source
Riddle and Closed book. (2016). Retrieved 2026, July 21, from https://thesaurus.plus/related/closed_book/riddle
Closed book & Riddle. N.p., 2016. Web. 21 Jul. 2026. <https://thesaurus.plus/related/closed_book/riddle>.
Riddle or Closed book. 2016. Accessed July 21, 2026. https://thesaurus.plus/related/closed_book/riddle.
Google Ngram Viewer shows how "closed book" and "riddle" have occurred on timeline