sitting up all night; staying up all night
Idiomatic phrase describing staying awake through the night, often with a sense of effort or vigilance. Used adverbially with verbs like 働く, 看病する, or 勉強する.
Before the exam, I studied all night without sleeping.
The nurse stayed up all night caring for the patient.
A fixed expression combining 夜 (night), 目 (eye), も (even), and 寝ず (negative continuative of 寝る, 'to sleep'), literally 'without even the eyes sleeping at night'. The exact origin is uncertain, but it is a traditional idiomatic phrase.