Synonyms of closed book

closed book

noun

as in mystery

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

• mystery
• puzzle
• enigma
• secret
• riddle
• why
• conundrum
• mystification
• problem
• puzzlement
• challenge
• matter
• head-scratcher
• trouble
• poser
• perplexity
• case
• knot
• stumper
• brainteaser

Example Sentences

Recent Examples of closed book

Alex Steel, the director of teaching strategy and a professor of law at the University of New South Wales, said a number of universities across Australia have announced a move back to closed book exams. — Samantha Murphy Kelly, CNN, 19 Jan. 2023

And there’s reason to believe that Kirchick sees this history as a closed book, a chapter that now belongs to the past. — Samuel Clowes Huneke, The New Republic, 8 June 2022

Readings of Alwyn as a closed book could be down to him being interviewed by people who aren’t used to encountering his English sensibility. — Louis Staples, Harper's BAZAAR, 17 May 2022