A moat, walled ditch, or hedge sunk in the ground to serve as a fence without impairing the view or scenic appeal.
暗墙;隐篱用来作栅栏,但又不阻碍视线或景观的护城河,或由墙围住的沟或陷入地中的篱笆
Her mind was walled in by fears.
恐惧攫住了她的心。
Don't worry, the prisoners are safely walled in and can't escape.
别担心,囚犯都被牢牢地关在围墙里,逃不了的。