On Saturday, President-elect Barack Obama asked, "What's a half-smoke?" at Ben's Chili Bowl in Washington, D.C.
To answer your question, Mr. President-elect, a half-smoke is basically a processed meat tube that's a lot plumper than your average hot dog (about twice the girth) with more of a spicy kick (look for the red pepper flakes inside).
Where does the "half" come from? A few theories exist, as explored in a comprehensive article from the Washington City Paper in 2007. It's only smoked halfway. It's cut in half when on the grill. It's often made from equal portions of beef and pork.
Ben's signature half-smoke comes smothered with chili, but it's perfectly acceptable to go the mustard-and-onions route. Besides Ben's, the sausage is sold all over the city, especially from street carts along the National Mall. Part of me is convinced that so many CVS pharmacies exist in the District for easy access to an important half-smoke chaser: Tums.