Jay Z -- I'm Always Big Pimpin' ... Just Don't Tell The Jury

Jay Z raps about being a "pimp in every sense of the word" -- but in reality, Jigga wants to keep his fat pockets and criminal past under wraps when it comes to his court battle over "Big Pimpin'."

Jay filed docs asking a judge to keep his wealth from the eyes of the jury hearing his illegal sampling lawsuit. He's being sued by a man who claims Jay lifted an Egyptian composition for the 2000 mega-smash hit. In the docs, Jay Z says his bank account and rap sheet have nothing to do with the case.

The plaintiff claims Jay stole the tune, so that makes the rapper's criminal past relevant.

The judge is still deciding what he'll allow in court.