開ひらき癖ぐせ

noun

warp that makes a book splay open

Refers to a physical defect in a book's binding or cover that causes it to open by itself or not stay closed. Often used in book-collecting or book-repair contexts.

• この文ぶん庫こ本ぼんは開ひらき癖ぐせがついていて、手てを離はなすとすぐに開ひらいてしまう。

  This paperback has a warp that makes it splay open as soon as you let go.

• 開ひらき癖ぐせを直なおすには、重おもしを乗のせてしばらく置おくといい。

  To fix a book that splays open, it's good to put a weight on it and leave it for a while.