In my world, a kebab is meat and veggies on a skewer. Falafel is the chick-pea stuff usually served in a pita. I suppose if I were ordering it from a street cart, I'd ask for "a falafel" if I meant some of that stuff in a pita, same as if I ordered a hot dog, I'd expect a wiener in a bun.
In my house growing up, we used "hot dog" to refer to both the wiener itself and the wiener in a bun. ("Go to the supermarket and pick up a package of hot dogs.") Not so with hamburgers, though. A ground beef patty on a bun was "a hamburger," but the ground beef itself was "hamburg."
Nachos for me definitely means tortilla chips covered with stuff -- melted cheese at the very least. But there's a bar near Bagman that serves its own version of nachos: homemade potato chips covered with cheese, meat, refried beans, jalapenos, sour cream ... darn, now I'm hungry.
