Dunch refers to a meal enjoyed subsequent to lunch but prior to dinner.
Dunch should be distinguished from linner, another meal occurring in the post-lunch, pre-dinner interval, in that dunch occurs after linner, closer to dinner time.
Thus, the socially accepted norm with regard to afternoon eating agendas comprises the following progression of meals:
Lunch --> Linner --> Dunch --> Dinner
A: "...I'd love to but I have to take a horrendous dunch." I'll see you at the 3:00 meeting."