The Jargon File (version 4.4.7, 29 Dec 2003):

great-wall
 vi.,n.

    [from SF fandom] A mass expedition to an oriental restaurant, esp. one
    where food is served family-style and shared. There is a common heuristic
    about the amount of food to order, expressed as ?Get N - 1 entrees?; the
    value of N, which is the number of people in the group, can be inferred
    from context (see N). See oriental food, ravs, stir-fried random.