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A person who is half-Mexican and half Irish. They have the awesomeness and ability to drink of the irish and the mexicans capacity to do hard labor.
Joe: Hey nick, look at the damn Mexican sitting outside the 7-11 waiting for work. Maybe we should pick him up and then drop him off at the police station.
Nick: You moron he's not a Mexican, he's a McMexican.
Joe: Oh well in then in that case let's buy him lunch.
by Bigcoolsean October 04, 2009