clear”是“清楚”，“mud”是“泥巴”，as clear as mud引申为莫名其妙；难以理解；不清晰；混乱。

【例句】

Oh well, that's all as clear as mud, then.

哎呀，那么一来这真是成了一本糊涂账了。

Unfortunately, it is impossible to predict a political process that is as clear as mud.

然而遗憾的是，想要预测混沌不明的政治进程是不可能的。