密不透風 mì bù tòu fēng

DEFINITIONS

  1. sealed off
  2. impenetrable

CHARACTERS

密 mì
HSK 4
dense, thick, close; intimate
不 bù
HSK 1
no, not; un-; negative prefix
透 tòu
HSK 5
penetrate, pass through
風 fēng wind; air; manners, atmosphere