fourthmeal
n.— «Taco Bell has in recent years promoted its late-night hours and coined the term “Fourthmeal” to denote a late-evening meal.» —“On the Menu: Fast-food outlets open later” by Keith Roysdon Star Press (Muncie, Indiana) June 14, 2007. (source: Double-Tongued Dictionary)
Is this something like “second breakfast?”