There are 2 different types of binges. From _The_Overcoming_Bulimia_Workbook_ by McCabe, McFarlane, and Olmsted.
Objective Binges:An Objective Binge involves eating, within a specific period of time (usually less than 2 hours), an amount of food that is considered large compared to what most people would eat in the same situations.
(comments by Jen: Large = 2000 calories and up. 10000 calories is not unusual. There are times when healthy eaters will eat 2000 calories in one sitting.)
Subjective Binges:A Subjective Binge occurs when a person eats and feels out of control, but the amount of food consumed is not large.
(comments by Jen: like a grape. The idea here is that the eating session is perceived as a binge by the person eating. Yes, it's a distortion, but it is still a binge.)