積ん読
Tsundoku
つんどく
A clever wordplay combining 積む (tsumu = to pile up) and 読 (doku = reading). It sounds like 積んでおく (tsunde oku = to leave something piled up), with 読 swapped in. The word has existed since the Meiji era and describes the universal experience of buying books with every intention of reading them... and then just watching them stack up. The sound of the word itself evokes the image of books piling higher and higher. It has become one of the most well-known "untranslatable Japanese words" in English-speaking countries — you will find it in countless "beautiful Japanese words" listicles.
Examples
また本買っちゃった…積ん読がどんどん増える
I bought another book... my tsundoku pile just keeps growing.
Self-deprecating after an impulse buy at the bookstore
積ん読100冊超えてるのにまた買うの？
You already have over 100 unread books and you are buying more?!
Calling out a book-loving friend
積ん読を消化するために今月は本屋に行かない宣言
I am declaring a bookstore ban this month to work through my tsundoku.
Kindleにしても積ん読は減らないということがわかった
Turns out switching to Kindle does not solve the tsundoku problem.