From Longman Dictionary of Contemporary Englishdinerdin‧er /ˈdaɪnə $ -ər/ ●○○ noun [countable] 1 DFEATsomeone who is eating in a restaurant2 especially American EnglishDF a small restaurant that serves cheap meals
Examples from the Corpus
diner• Etiquette requires more or less continuous competition among diners to keep one another's tea-cups topped up.• He was known in every bar and diner in town, and tolerated in most.• It is now established as a healthy food, with popular appeal for the ever-growing numbers of health-conscious diners.• But now, along with high drama, diners at Checkers can enjoy a lighter menu.• For diners on any kind of restricted diet, this is an invaluable service.• Now the gluttonous diner has a wide array of eateries from which to choose.• The two link up later, however, at a roadside diner.• The forks of the diners flash from plate to mouth and back.From Longman Business Dictionarydinerdin‧er /ˈdaɪnə-ər/ noun [countable] American English a small restaurant that serves cheap mealsShe’s a waitress in an all-night diner. 