Definition of "diner"

diner

/ˈdaɪnə(ɹ)/

noun
plural diners
1. One who dines.
  Quotations
  The most rapid and most seductive transition in all human nature is that which attends the palliation of a ravenous appetite. […] Can those harmless but refined fellow-diners be the selfish cads whose gluttony and personal appearance so raised your contemptuous wrath on your arrival?
  1922, Ben Travers, chapter 5, in A Cuckoo in the Nest
  When it comes to Chinese food I have always operated under the policy that the less known about the preparation the better. A wise diner who is invited to visit the kitchen replies by saying, as politely as possible, that he has a pressing engagement elsewhere.
  1983, Calvin Trillin, Third Helpings
2. A dining car in a railroad train.
  Quotations
  Pacific No. 60123, H. A. Ivatt, a Leeds engine with 12 corridors, but no diners, went by, however.
  1951 January, R. A. H. Weight, “A Railway Recorder in Essex and Hertfordshire”, in Railway Magazine, page 46
  The diner is everybody's kitchen.
  1979, Richard Gutman, American Diner
3. (US) A typically small restaurant, usually modeled after a railroad dining car, that serves lower-class fare, normally having a counter with stools along one side and booths on the other, and often decorated in 50s and 60s pop culture themes and playing popular music from those decades.