It was a Masonic sign Caderousse had taught him.是什么意思？

It was a Masonic sign Caderousse had taught him.

这是卡德罗斯教他的暗号.

it

pron. 它，他，正好是所需的，事实[情况]；n. <美俚>傻瓜，笨蛋，<俚>绝妙的人，理想的东西，登峰造极；

例句
I suggest you leave it to an expert...
我建议你把它留给专家来解决。

was

v. 用来表示某人或某物即主语本身，用来表示某人或某物属于某一群体或有某种性质（ be的过去式 ），在，存在，不受干扰；

例句
There was a terrible sadness in her eyes...
她眼神中流露出深深的悲伤。

masonic

adj. 共济会会员的；

例句
My father would occasionally go to his Masonic lodge.
我爸爸偶尔会到他的共济会分会那里去。

sign

n. 符号，手势，迹象，指示

例句
...a crime wave that shows no sign of abating.
丝毫没有减弱迹象的犯罪势头

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。

taught

v. 教( teach的过去式和过去分词 )，教书，训练，教育；

例句
The way that American history is taught may change in order to accommodate some more of those cultures.
美国历史的授课方式可能会为了照顾到更多的文化而作改变。

him

pron. (he的宾格)他；

例句
They said goodbye to him as he got aboard the train at Union Station.
当他在联合火车站登上火车之际，他们向他道别。