Hiding narcotics or other objects in one's butt. This comes from the Toy Story movies in which Mr. Potato Head stores objects in his rear compartment.
At the airport the dealer was potato heading in order to keep his drugs safe from the security.
The act of transporting drugs, weapons, and/or any illegal item in your ass, someone else's ass, or Mr. Potato Head's ass
Watch out man, the cops are sniffin' everyones assholes for anyone who is potato heading