idiosyncratic reading; peculiar pronunciation of a kanji or compound
Refers to a non-standard or unexpected way of reading a kanji or compound, often due to habit, dialect, or historical usage. Common in discussions of Japanese orthography and language learning.
This kanji has an idiosyncratic reading, so you need to be careful.
He has a habit of reading 雰囲気 as ふいんき (instead of the standard ふんいき).
Compound of 読み (yomi, 'reading') and 癖 (kuse, 'habit'). The exact historical derivation is uncertain, but the term naturally describes a habitual or peculiar way of reading.