What kind of idiot said this to you?
It's supposed to be said like this: 'Ks Omak ya Ibn el Lbwa' or 'Ks Omak ya Ibn el Mara el Lbwa'.
So, after you punch him the face for saying it, teach him how to say it correctly. And its meaning is a bit too offensive for me to Translate as it is not even considered a Classy Insult and I don't like to go down to the level of explaining such crap. Don't get me wrong though, I will use it incase I have to.