關公面前耍大刀 [关－－－－－－]

Jyutping gwaan1 gung1 min6 cin4 saa2 daai6 dou1
Pinyin guān gōng miàn qián shuǎ dà dāo

Definitions (Wiktionary)
  1. phrase, idiomatic
    to show off in front of an expert
    (syn.) 班門弄斧, 班门弄斧

關公面前耍大刀 [关－－－－－－]

Jyutping
Pinyin guān gōng miàn qián shuǎ dà dāo

Definitions (CC-CEDICT)
  1. lit. to wield the broadsword in the presence of Lord Guan (idiom)
  2. fig. to make a fool of oneself by showing off in front of an expert