閉關

to close the passes / to seal off the country / seclusion (monastic practice, e.g. of Chan Buddhists)

to close / to stop up / to shut / to obstruct

mountain pass / to close; to shut; to turn off / to confine; to lock (sb) up; to shut (sb in a room, a bird in a cage etc) / to concern; to involve

close the country to international intercourse

to close the passes and seal off the country / to close a country to exclude foreign contact

closed-door policy