want some piece of me

i heard someone saying that..
what does that mean?
i looked up that expression in dictionary but cant find it

*points to my butt*

You want a piece of this, huh punk? Come on, I'll give you a piece of this.

It also means to want someone. like to fuck someone

It is usually challenging someone to a fight. Like ''You wanna fight me?''

If it's used in a sexual manner the person will say something like ''I'd like a piece of that(meaning a girl)''.

I can't believe you never heard that in movies!

It's "want a piece of me" not "want some piece of me".