1 To escape; to vanish or disappear. (Not necessarily in a southerly direction.)

去逃跑；逃走不见或消失（并不一定是往南逃）

例：

Everyone in the gang went south when they learned that the police had discovered their hideout.

那帮人听说警察发现了他们的藏身之处，便纷纷逃走不见了。

The dog has gone south into the night.

狗已消失在夜色中了。

2 To fall or drop; to depreciate; to lose quality or value. (Especially related to finances or stock exchanges.)

下降或落下；贬值；失去质量或价值(尤指与金融或股票交易有关的。)

这个意思可能和地图上的“上北下南”有关，南方就是下方，往南走就是下降的趋势。

例：

The company's stock profile continued going south for the third day in a row today.

该公司的股票今天连续第三天下跌。

It seems like all our moral standards have just gone south.

看来我们的道德标准都下降了。

3 To cease working or functioning; to quit, fail, or fall apart.

停止工作或运作；退出，失败或分崩离析。

例：

Talks between the labor union and the construction firm went south yesterday, so it looks like workers will be on strike again soon.

工会和建筑公司昨天谈崩了，所以看起来工人很快就会再次罢工。

My computer is only a month old, and it's already gone south.

我的电脑才用了一个月，就已经坏了。

总的来说，go south都有一个趋势上的不好，由此我们也可以猜出go north作为它的反方向也就表示了一个好的趋势。

例：

I hope the talk will go north this time.

我希望这次的会谈取得成功。