The term, "Haystack" is used as a name for a food often served at vegetarian and vegan lunches and dinners. It usually consists of Frito's (or whatever chips desired, often smashed), beans, lettuce, tomatoes, onions, sour cream, salsa, and cheese (often times a vegan supplement is used). This dish is most commonly served at Seventh-day Adventist schools and potlucks. But it's really just a taco salad.
"I am craving a haystack!"
"What's a haystack?"
"The Adventist version of a taco salad."