Jyutping
fai3 cam2 mong4 sik6
Pinyin
fèi qǐn wàng shí
Definitions (CC-CEDICT)
to neglect sleep and forget about food (idiom)
to skip one's sleep and meals
to be completely wrapped up in one's work
Definitions (粵典–words.hk)
動詞
形容好投入一件事，可以連食飯同瞓覺都唔理 to forget to eat and sleep since one is completely absorbed in working
為咗入大學，佢呢半年都廢寢忘餐噉讀書。
为咗入大学，佢呢半年都废寝忘餐噉读书。
wai6 zo2 jap6 daai6 hok6, keoi5 ni1 bun3 nin4 dou1 fai3 cam2 mong4 caan1 gam2 duk6 syu1. For the sake of entering university, he was totally absorbed with his studying in the last six months, neglecting meals and rest.
參看
廢寢忘餐
Definitions (Wiktionary)
phrase, idiomatic
to be completely wrapped up in one's work and skip one's sleep and meals