Pseudonym or "code word" for "carding." Commonly used when an underage person is present in a bar and needs to ask the question: "Are they carding?" By replacing the term "carding" with "hotdogging," the underage individual avoids being discovered.
Underage person (Skippy): "Are they hotdogging tonight?"
Person of legal drinking age (Scott): "Nah dude, you're totally fine."