Jungler = The player you blame when you lose your lane, if there is one on your team (you can identify a jungler by his use of the summoner spell 'smite'
Feeding = Doing slightly worse than the person using the word in the K/D/A board.
Farm = The act of planting, growing and harvesting foodstuffs and other perishable goods from the earth. Also, wildly auto-attacking minions non-stop in the hopes that you get gold out of one or two minions a wave.
MIA = Something you say when the enemy in your lane is gone so you don't get blamed when they get a double kill in another lane (which they will anyway).
GG, Noobs = I was carried by my team to victory and I'm very, very happy about it.
Easy = See 'GG, Noobs'. Alternate Definition: This 55 minute, incredibly even back and forth game that could have gone either way right up until the end sure was fun, ey guys?
SS = How European socialists say MIA to excuse themselves from blame when the person from their lane gets a double kill in another lane.
Instalock = The correct way to choose champions. You can more Elo for a win and lose less from a loss the faster you lock your champion at the select screen.
Teamwork = Assuming that the four other people on your team wear drool bibs and convincing yourself that only your elite e-peen can carry the group to victory. Proper teamwork is you behaving like Rambo and then complaining that no one follows you.
Tank = Someone who runs into the middle of the enemy champions, eats all their CC and dies while the rest of the team hugs the tower and fights over a single minion wave. Often also guilty of feeding.
Support = A mini-game within the larger game of LoL akin to gambling, where you're betting 20-60 minutes of your life and some Elo that the person you share a lane with isn't functionally retarded. The odds of this being the case and you actually winning hover around 80/20 against.
Map Awareness = Being near the crazy person on your team whose in the enemy jungle with all three of your front towers down when he gets jumped by the enemy team. usage example: "Fuck you <name>, no map awareness at all."
GG (in team chat) = i'm Going to stop trying now, Guys.
GG, WP = I have no idea. No one in LoL seems familiar with this phrase.