closed book

A subject, person, or topic that is difficult to understand, know about, or interpret; something that is completely unknown or mysterious to someone.

ruТема, человек или предмет, который трудно понять, узнать или истолковать; нечто совершенно неизвестное или загадочное для кого-либо.esPersona, tema o asunto difícil de entender, conocer o interpretar; algo completamente desconocido o misterioso para alguien.frUne personne, un sujet ou une chose difficile à comprendre, à connaître ou à interpréter ; quelque chose de totalement inconnu ou mystérieux pour quelqu'un.deEine Sache, ein Mensch oder ein Thema, das schwer zu verstehen, zu durchschauen oder zu deuten ist; etwas völlig Unbekanntes oder Rätselhaftes für jemanden.ptAssunto, pessoa ou coisa difícil de entender, conhecer ou interpretar; algo completamente desconhecido ou misterioso para alguém.zh指难以理解、了解或解释的人、事物或主题；对某人来说完全未知或神秘的东西。arموضوع أو شخص أو شيء يصعب فهمه أو معرفته أو تفسيره؛ أمر مجهول تمامًا أو غامض بالنسبة لشخص ما.

1. Mystery or unknown B2 informal

   A subject or person that is difficult to understand or know about.

   • His past is a closed book to everyone.
   • Quantum physics is a closed book to me.
   • She remains a closed book, even to her closest friends.

   ruТайна или неизвестностьeslibro cerradofrLivre fermédeRätsel oder UnbekanntesptMistério ou incógnitazh谜或未知事物arسر أو مجهول

2. Finished matter B2 informal

   A topic or issue that is no longer being considered or discussed.

   • That argument is a closed book; let's move on.
   • The investigation is now a closed book.
   • For the team, last season's failure is a closed book.

   ruЗакрытая темаesasunto cerradofraffaire classéedeAbgeschlossene SacheptAssunto encerradozh已了结的事arموضوع مغلق