Take The Piss
A British idiom that means teasing or joking. To “take the piss” is to joke around, to “take the piss out of someone” is to tease them.
It’s the equivalent of the American phrase “mess with” or “screw round with.”
There are many conflicting stories of its origin.
Why I Looked It Up
I spent three days in London. I heard it more than once. I had heard it before, and didn’t have a clue what it meant.
Update
Added on
In Eminem’s book The Way I Am, he writes:
I think one of the things I like to do in my songs – like in “My Name Is,” for example – is take the piss out of myself before anyone goes at me.