"Eighty-six" is a slang term that means to get rid of something or to cancel a previous order or decision. The past tense form, "86-ed," is also commonly used.
In the restaurant business, the term "86" is used to indicate that an item is not available. For example, to say "86 on prime rib" means that the restaurant has no prime rib to serve at that time. Customers who are refused service are also said to have been "86-ed."
In addition to the restaurant business, one possibility for the word's origin is the U.S. Navy, where AT-6 (pronounced "eighty-six") was the term used to describe a ship part that would be discarded.