An abbreviation for the phrase "Got to masturbate", used in similar situations as the term "g2g"
Female: I'm extremely horny right now, omg...
Male #1: I could totally fix that for you!
Female: No worries, my husband will be home soon.
Male #1: Damn :(
Male #2: That sucks dude.
Male #1: g2m, be back in 15.