A phrase used to describe something particularly awful. Similar in usage to words like: bad, terrible unpleasant. Originated from people being too lazy to type the word "Garbage". It was then picked up by gamers who used the jazzed up version over Ventrilo (vent).Usually used when describing the nature of an unpleasant event or occurrence.
Dude1: "How'd you do on your final?"
Dude2: "ahh man I did gar gar"
"Ganked at grom'gol base camp, wow thats fuckin' gar gar."