A phrase created by 2 University of Waterloo students in 2012.
The phrase refers to the often explosive bowel moments caused by the use of Mass Gainer supplements and used as a code word.

*Note these guys used 8-12 scoops of Mass Gainer a day, however they also trained very intensely and made significant gains. Drinking Mass Gainers without a proper workout regiment will mostly result in many MGMs and belly fat as well.