Players in their chosen video game who try too hard and sweat it out all day and night causing obsessive behaviour leading to fatness, loneliness, unemployment and benefit claims so they can stay home and play games all day. Sweaters can usually be be spotted by their particularly high multiplayer rank and by solving a simple equation, it is possible to conclude how much of a sweater they are:
(Multiplayer Rank/Number of Days Since Launch) x Average XP per round of game
Another way to spot potential sweaters is nonsensical, ostentatious online handles. Scientists believe that due to a lack of sunshine, good nutrients and normal, social interaction, sweaters spoken and written language skills diminish greatly, sometimes irreversibly.
Sweaters can be found in the usual sweater breeding grounds on games such as Gears of War (2), Call of Duty, FIFA etc. It is also apparent that when sweaters meet online, they will form a group known as a 'pool'. A pool can be devastatingly irritating to play against, but remembering that you are not fat, unemployed and a virgin usually counters this irritation.
Fred: Wow, four level 100s on the opposition team this round
Harry: Yeah, looks like another pool of sweaters
Gary: Jesus, a nuke in under 3 minutes, that guy must be proper sweating it.
Jules: Yeah it's his 4th nuke in 6 games, he must be heading down to Boots for some more antiperspirant when his benefit money comes through