get nasty到底什么意思

例句
That is when things could get nasty.
那时候这个世界可能就不安全了.
Those merchants can get nasty.
那些商人不会轻饶我的.
He says when things start to get nasty."If you can't work with them,we'll just have to replace you!"
当事情变得糟糕时,他就会这么说,“如果你不能和他们合作,我们只能把你换掉!”