不知輕重 [－－轻－]

Jyutping bat1 zi1 hing1 cung5
Pinyin bù zhī qīng zhòng

Definitions (CC-CEDICT)
  1. lit. not knowing what's important (idiom); no appreciation of the gravity of things
  2. naive
  3. doesn't know who's who
  4. no sense of priorities