JAY-Z recorded an entire album, American Gangster, in homage to notorious Harlem drug lord Frank Lucas.

He also called Lucas a snitch.  Lucas passed away at 88 last year.  His son Frank Lucas Jr was asked about Hov labeling his dad the S word in light of the fact that JAY's Roc Nation COO Desiree Perez was a DEA informant.

According to Lucas Jr., he was in the truck when his wheelchair-bound dad pressed JAY-Z about his words and turned Hov into a "mumbling idiot."  He also ripped JAY for tearing down his pop's legacy.

"Not only are you betraying a black man's legacy," Lucas Jr. said.  "But you sucked off the legacy and then betrayed it.  Your position is supposed to ensure that we get equal opportunity.  You are supposed to make sure the man's story isn't dead and told correctly ... when all is said and done if you're going to say something say it in a factual fashion."

Frank Lucas was, in fact, a federal informant.