老虎唔發威當病貓 [－－－发－当－猫]

Jyutping lou5 fu2 m4 faat3 wai1 dong3 beng6 maau1
Pinyin lǎo hǔ wú fā wēi dāng bìng māo

Definitions (CC-CANTO)
  1. a tiger taken as an ill cat just because it doesn't roar, a metaphor to say don't underestimate one's power