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Jyutping waa6 dou1 mou5 gam3 faai3
Pinyin huà dōu mǎo hán kuài

Definitions (粵典–words.hk)
  1. 語句
    好快​;​嘢​都​未​講完​就​已經​完成​、​發生
    happened quickly; very fast; literally: to happen faster than it is spoken
  2. 參看
    話咁快、話冇咁快
Definitions (Kaifangcidian)
  1. 說時遲那時快 – 说时迟那时快

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Jyutping waa6 dou1 mou5 gam3 faai3
Pinyin huà dōu mǎo gān kuài

Definitions (CC-CANTO)
  1. so fast; before you know it; no sooner said than done
Examples (粵典–words.hk)
  1. Cantonese
    啱啱网上订咗只表,话都冇咁快就送到。
    啱啱網上訂咗隻錶,話都冇咁快就送到。
    ngaam1 ngaam1 mong5 soeng6 deng6 zo2 zek3 biu1, waa6 dou1 mou5 gam3 faai3 zau6 sung3 dou3.
    • I just ordered a watch online, and before I knew it, it was delivered to me.
  2. Cantonese
    仲谂住开完会同佢倾多两句,点知佢话都冇咁快就走咗。
    仲諗住開完會同佢傾多兩句,點知佢話都冇咁快就走咗。
    zung6 nam2 zyu6 hoi1 jyun4 wui2 tung4 keoi5 king1 do1 loeng5 geoi3, dim2 zi1 keoi5 waa6 dou1 mou5 gam3 faai3 zau6 zau2 zo2.
    • I wanted to speak with him after the meeting was over, but he was gone in a flash.