Synonyms of closed books

closed books

noun

plural of closed book

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

• mysteries
• puzzles
• secrets
• enigmas
• riddles
• mystifications
• problems
• whys
• matters
• conundrums
• challenges
• puzzlements
• head-scratchers
• troubles
• perplexities
• posers
• cases
• knots
• stumpers
• brainteasers