noun. A substantial instance of dumping, whether of significant others or God-given feces.
Real citation: "So, did anybody hit this during last season's Tahoe megadumpage?"
(bad_roo, Sept. 10, 2005, http://www.tetongravity.com/forums/archive/index.php?t-34868.html)
Made-up citation: "As a summer camp counselor for disabled children, I cleaned up the mightiest megadumpage in the land. And a shitstorm or two."