I was wondering the same thing. It is known to be slang for excretion (shit, to be more blunt), and of course you have pap smears which test for abnormalities in the cells of a woman's cervix.
PAP is an acronym that stands for many political organizations to include,
Pan-African Parliament - a legislative body of the African Union
Partido Aprista Peruano - a political party in Peru
People's Action Party - a political party in Singapore
People's Armed Police - Police force in China
Provincial Assembly of the Punjab - the house of representatives in Pakistan
PAP is also the IATA airport code for Port-au-Prince International Airport in Haiti. Pap is also the name of a village in northeastern Hungary as well as a city in Uzbekistan. Pap is the nickname of Mike Papantonio from Air America, but then again we already covered excrement.

Pap Finn was Huck's father in Mark Twain's Adventures of Huckleberry Finn.
As far as biological and medicinal acronyms you have
Polyadenine polymerase - an enzyme involved in messenger RNA processing
Polyadenylate polymerase - another enzyme involved in creation of mRNA tails
Positive airway pressure - a method of respiratory ventilation used primarily in the treatment of sleep apnea
Prostatic acid phosphatase
Pulmonary Arterial Pressure
Purple acid phosphatases
And finally, in the world of Technology you have even more acronyms for PAP
Password authentication protocol - q method for identifying computer users to a remote server
Picture and Picture - two image sources displayed side by side on a television screen
Plastic Animation Paper - 2D animation software
Plug-and-play - automated computer hardware configuration
Push Access Protocol - part of the Wireless Application Protocol suite
PEX-AL-PEX - a special type of Cross-linked polyethylene (PEX) pipe with the additional layer of aluminum
So, back to Steve's question? What the hell did this guy mean by a pap?? I've no idea.