Wildsau is a German loan word which literally means "wild soar" but does not necessarily refer to the zool. definition of the word. Instead, it is used mostly expression for a person that's wild one way or the other, where the context could be anything, e.g. from the girlfriend ("she's an animal in bed") or another driver ("he drives like crazy").
Why are you so exhausted? - My new girlfriend is a true Wildsau.
You drive like a Wildsau.