Ranch dressing is an American salad dressing made with buttermilk, mayonnaise, garlic, onion and herbs, typically including chives, parsley, and dill. It has been the best-selling salad dressing in the United States since 1992.
The term "ranch" is sometimes used in American cooking to refer to a dairy-garlic-and-herb flavor profile, in sauces, dips, potato chips, spice powders, etc. It is not to be confused with ranchero (or ranchera) sauce, which has a tomato-and-chili base from Mexican cuisine.