She babbled a few words to him.

她对他说了几知所云的话。

This essay hardly makes any sense, it's neither rhyme nor reason.

这写得伦类, 简直知所云。

That sounds like fiddle-faddle double-talk, but I don't know any less recursive way to say it.

这听起来似乎很无聊，知所云。但是，我知道太绕口的说法。