Idiom of the day :- A closed book

Usage, examples and definition of the Idiom :-

‘I am supposed to know just about everything,’ Professor Olson said, ‘so I can’t let anyone know that I have just come across something that is a closed book to me.’ As it is used here, a closed book is something – a topic, a subject, an idea – you don’t know anything about. ‘But I have to confess that physics is a closed book to me,’ the Professor said with a huge sigh.