壁壘森嚴

壁垒森严
bìlěisēnyán
  1. closely guarded
  2. strongly fortified
  3. sharply divided

CEDICT

strongly fortified

Wiktionary

堅固的防禦

維基詞典

Entry Composition

1 壁壘 bìlěi
  1. rampart
  2. barrier
2 森嚴 sēnyán
  1. strict
  2. rigid
  3. tight (security)