Not quite brunch, and not quite lupper. It's that one meal you have when you don't feel like cooking three times in the same day. It's pronounced exactly how it's spelled (which is rather hard either way).
The meal you eat in the late afternoon that has to serve as breakfast, lunch, and supper because you stayed out partying all-night and slept in all day.
Brupper is a meal combing breakfast and supper eaten in the middle of the night. The word is derived on the same principle as brunch, which is a meal in-between breakfast and lunch.
Traditionally, brupper includes gin and nachos, but may extend to party leftovers, crackers with cheese, or even just a bottle of vodka chilled in the freezer. Folk wisdom suggests that the combination of cheese and alcohol is an effective soporific.