That example doesn't make sense to me. How do you SLEEP ON a movie?

In this case it means "underestimate".

It doesn’t mean to underestimate in any context. It means to postpone. In a certain sense, if you’re postponing something, one possible interpretation might be that you’re not giving it the importance that it deserves. But I would never assigned the meaning of “underestimate” to this verb.

http://sleeping-on-me.urbanup.com/10342055 Check the first two items out.

Yeah, my little brother told me black kids use it.