壁垒森严

壁壘森嚴
bìlěisēnyán
  1. closely guarded
  2. strongly fortified
  3. sharply divided

CEDICT

strongly fortified

Wiktionary

坚固的防御

維基詞典

Entry Composition

1 壁垒 bìlěi
  1. rampart
  2. barrier
2 森严 sēnyán
  1. strict
  2. rigid
  3. tight (security)