What does ACP mean when it comes to rap?

Like in Lil Wyte or Three-6-Mafia songs "I'm ACP you can't see me" and so forth. No, I am NOT looking for the ammunition definition, or American College of Pharmacy or one of the dozens of other meanings, just the rap meaning. It is in hundreds of songs, from Chingy "GIB... ACP" to Three-6. Please help!