The acronym stands for the "Get High Movement," can be used interchangeably with getting high, wasted, drunk, etc. If you see this graffitied throughout your high school, you can be reassured that your school has been overrun with rich, bored druggie teenagers. Contrary to popular belief, the acronym does not stand for "Get High Montville" or any other town/school name beginning with an "M". Please do not be delusional. It is in no way supportive of the non-existent school spirit in your school. Also contrary to popular belief, it does not stand for the "Get Healthy Movement."
I was like so GHM when the cop pulled me over. LOL.