As United States Supreme Court Justice Potter Stewart best expressed during his "threshold test" for obscenity in Jacobellis v. Ohio (1964): "I know it when I see it".
And when I stare longingly and lovingly at a hot dog, I do not see a sandwich, but an American cuisine.
A bun-less hot dog is simply and historically a frankfurter. Our national treasure was invented at the Polo Grounds by Harry M. Stevens, a small business concessionaire, originally calling them Dachshund sandwiches. In a great American twist, a New York Post cartoonist couldn't spell dachshund, so he named and reclassified them as hot dogs, forever making them America's favorite concession item and not some foreign sandwich like a baguette or a croissant.
Do the right thing, Mr. President. Define a hot dog as a hot dog