Left over biscuits and yesterday's pork chop with some quickled onions & jalapeños.
i am a burger fanatic, so i would say that it’s a specific preparation of burger.
HOWEVER, because English is the way it is, words can have multiple uses/meanings, and one of the ways a word can get a new use/meaning is through common usage. this means that because people have used the word ‘slider’ to mean a small sandwich, then it BECAME that meaning.