The prisoners had escaped by tunnelling.是什么意思？

The prisoners had escaped by tunnelling.

犯人挖地道逃跑了.

the

art. 指已提到的人（物），指说话人与听者已知的人（物），用于独一无二的事物前，与形容词最高级和序数词连用；

例句
He did have a real knowledge of the country...
他对该国的确知之甚多。

prisoners

n. 囚徒( prisoner的名词复数 )，俘虏，被夺去自由的人[动物]等；

例句
The regulations were relaxed and the prisoners could get out and about a bit.
规定有所放宽，犯人可以出去短暂放风。

had

v. 有（ have的过去式和过去分词 ），（亲属关系中）接受，拿，买到；

例句
He claimed that his parents had abandoned him...
他声称父母遗弃了他。

escaped

adj. 溜走；v. 逃脱( escape的过去式和过去分词 )，（气体，液体等）漏出，（未受伤或只受了一点伤害而）逃脱，声音（不自觉地）由…发出；

例句
The gunman escaped on a motorcycle being ridden by an accomplice.
持枪歹徒坐上一辆由同伙驾驶的摩托车逃逸。

by

prep. 在…旁边，表示方式，由于，经过；adv. 经过，表示保留或保存时用，短暂拜访；

例句
...expensive make-up that we saw being advertised by a beautiful model...
我们所见的由一位漂亮模特代言的昂贵化妆品

tunnelling

n. 隧道效应，开挖隧道，掘进；

例句
A massive rock fall trapped the men as they operated a tunnelling machine...
这些工人在操作隧道挖掘机时被大量的落石困住了。