Here is a little refresher for the mmorpg veterans, and a few tips for the new players of mmorpg. From the site The Daedalus Project: a dictionary of commonly used terms in mmorpgs.

Here is a sample:

Aggro As a verb, it refers to a hostile mob that has noticed a player and is actively trying to attack that player. As a noun, it refers to the amount of “hostility” the player has generated on the mob. In typical combat strategy, the fighter tries to take as much aggro as possible away from weaker players such as healers and mages.

Their whole dictionary can be found here.
If you don't see something you use regularly, why not suggest it?