Abbreviation for Get Off Me, usually used by gamers after making a noob move (beginner, bad, or stupid mistake) having the equivalent of my bad, back off, or leave me alone. The full word is used by some gamers in RL as an inside joke.
"Dude, why didn't you snipe that noob, you just let him walk by and frag me, and I dropped the flag."
GOMS stands for 'Get On My Swing', originating from the well known swing-fetish. Most commonly used when seeing a very attractive person, but also used in other circumstances i.e. to express love for an object or more often a food.