JuicyJam
To work with someone to gain Xbox Live Achievements, and once you have obtained your goal, to abandon your fellow boosters and not help them in return
That time on Gears 3 when we were working on hammer strike kills and JuicyJams conviently left right after he got the achievement, this has become a well known term in the community, along with 'going full Chewy' as a reference to rage quitting