mega- + tour
megatour (plural megatours)
- (informal) A very large-scale or highly successful tour.
2015 October 15, Joe Coscarelli, “Poo Bear, Speaking Softly and Carrying a Bieber Comeback”, in New York Times[1]:Undeterred, Mr. Bieber soon offered to fly Poo Bear to the Miami stop of his yearlong “Believe” megatour.