a poo so massive that it clogs up the toilet and can not be glushed nor plunged. Usually the only way to get these bad boys down is by using hot water to break up the poo molecules.
I took such a megadump that the toilet at work was clogged up for three days until the janitors came in and removed it from the toilet manually.
by Squall January 03, 2004
German underground EBM band who released 5 albums from 1999 to 2004. Believed to be non-active as of 2009 though.
by gothic_hobbit August 23, 2009
Strictly speaking, a dump such that all the excrement would fill up 1,000,000 Standard high capacity Canadian toilets. (mega is the SI suffix for a million.) colloquially, it is a massive crap such that the defecator feels like he has just dropped the Fat Boy. Mofos with irritable bowel syndrome are notorious for releasing these and then bragging to their friends that they feel about 10 pounds lighter.
Craig: You took another megadump, didn't you? Now no ones going to be able to use it until the janitor gets it unclogged manually.
Bob: it wasn't me.... Uh... It was the guy before!
Bob: it wasn't me.... Uh... It was the guy before!
by Craptastic16 October 19, 2012