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1.
When a Mc Donalds Dollar menu Mc chicken is inserted into a Mc Double. Creating a Mc Monster. There is also a Mc Monster challenge where one cannot put down, drink or use a napkin once the contestant has started. This word originated from the Northwest of Washington.
Bill: Lets go to Mc Donalds to do the Mc Monster Challenge!
Joe: Oh god! im still recovering from the last Mc Monster
by 221krew June 08, 2010
 
2.
Someone of large physical size who eats at McDonald's frequently.
We were walking out of McDonald's, when, suddenly, a McMonster driving a Ford minivan almost ran us over trying to drag race out of the drive-thru!
by Fred Murphy9999 August 31, 2010
 
3.
Extremely large breasts
Look at Maki's McMonsters, there huge!
by Maki Mcmonster January 17, 2009