closed book

closed book

n. One that cannot be known or understood.

closed book

n 1. something deemed unknown or incapable of being understood 2. a matter that has been finally concluded and admits of no further consideration

Thesaurus

Noun

1.

closed book - something that baffles understanding and cannot be explained; "how it got out is a mystery"; "it remains one of nature's secrets"enigma, mystery, secretperplexity - trouble or confusion resulting from complexity