sealed book

noun

1. something beyond understanding and therefore unknown.

sealed book

noun

1. See closed book
   another term for closed book

Word History and Origins

Origin of sealed book¹

First recorded in 1810–20

Example Sentences

Old and new measurements, tonnage, time allowances and movable ballast, are all a sealed book to me.

From Project Gutenberg

But, if you come to look at the matter closely, you will see that the time present is also in some sense a sealed book to us.

From Project Gutenberg

And yet, in spite of it all, Judeo-German has remained practically a sealed book to the world.

From Project Gutenberg

Monsieur Calonne had read my inmost heart, whilst I foolishly imagined it was a sealed book!

From Project Gutenberg

From this cause the characters of those nearest and dearest to him remained to his life's end a sealed book.

From Project Gutenberg