ad grat
n.— «Ad grat, or auto grat, as it’s know in the biz, is a restaurant standard that means gratuity is automatically added to a check. Generally the gratuity is 18 percent, it’s added on the pre-taxed total for large parties (between six and eight or more) and the restaurant should note on their menu if they practice this policy.» —“Eat Beat” by Karri Peifer Richmond.com (Virginia) Aug. 26, 2005. (source: Double-Tongued Dictionary)