a closed book
a closed book
a thing of which you have no knowledge or understanding
1944 - Frank Clune - The Red Heart - The desert is an open book to the man of the Vast Open Spaces, but to the schoolmaster it was a closed book.
Related Idioms :
behind closed doors
(of an action) done in a secretive or furtive way hidden from public view
a closed book :
Idioms Index – Previous Page
Related Links : a closed book