autograt
n.— «An autograt is an automatic gratuity of usually 15 to 20 percent assessed to larger tables, usually of 6 people of more. an autograt affords the waiter the luxury of knowing his/her tip is a fait accompli. some diners tip on top of autograts.» —“Autograt” by timesnewroman Waiter Blog Dec. 1, 2004. (source: Double-Tongued Dictionary)