abbreviation of "Generic Mexican". Those girls and guys who wear the stretchy headbands, big t-shirts, capris, big shoes with the tongue sticking out all the same color. They act the same, talk the same, walk the same, they are the same! Can be seen in both genders and multiple ages from 5-50. It is a virus people.
* White people can be GM's as well.
Morty: Wow that girl Kelly is white but she's ghetto...
Northrup: dude she's a GM and a GM lover!