In my misspent youth, I once worked a summer job as a waiter at Shoney's. It is an experience that I do not recommend. But it did teach me two valuable things: 1) How not to drown in a puddle of my own embarrassment when marching around the dining room with my fellow servers and singing a birthday song that began, "Happy, happy birthday, we're so glad you came"; and 2) That when the surly line cooks ran out of chicken fried steak, they would shout "86 the chicken fried steak!" through the pass.
To "86" something, in restaurant slang, is to say that it is out, finished, gone, through, not on the menu anymore. This is the only sense in which I have heard the term used in my entire life.
But according to Wikipedia, which naturally has an entry about the term, two further meanings do exist. "86" can also be applied to people a restaurant refuses to serve, and some slang dictionaries say it can refer to murder.