水過鴨背 [－过鸭－]

Jyutping seoi2 gwo3 ngaap3 bui3
Pinyin shuǐ guò yā bèi

Definitions (Kaifangcidian)
  1. 善忘
  2. 健忘
  3. 不專心 – 不专心
  4. 全忘了
  5. 漫不經心 – 漫不经心
  6. 記憶力差 – 记忆力差
  7. 聽不進去 – 听不进去
  8. 記不起來 – 记不起来

水過鴨背 [－过鸭－]

Jyutping seoi2 gwo3 aap3 bui3
Pinyin shuǐ guò yā bèi

Definitions (CC-CANTO)
  1. describes a situation where someone has not paid any serious attention in learning or studying or in what he/she is saying and eventually cannot recall anything afterwards; to be forgetful
Definitions (粵典–words.hk)
  1. 語句
    話​人​聽​嘢​，​尤其​係​聽​書​嗰​陣​，​唔​留心​，​聽​完​都​冇​印象
    used to show that someone is not attentive, especially during lessons, thus remembering nothing told afterwards
  2. 近義詞
    左耳入右耳出
Definitions (Wiktionary)
  1. phrase, idiomatic
    like water off a duck's back