noun
A direct loanword used in Japanese to refer to the feeling of disappointment when one's idealized beliefs are shattered. Often used in literary or psychological contexts.
彼の不正を知って、大きなディスイリュージョンを感じた。
I felt a great disillusion upon learning of his dishonesty.
幻滅 is the native Japanese equivalent, more commonly used in everyday speech. ディスイリュージョン carries a slightly more literary or psychological nuance.
Borrowed from English 'disillusion'.