The MMO Gaming Dictionary is an ongoing project here at Bright Hub. It was originally begun on my blog, Muckbeast. It has been expanded here on Bright Hub and is updated periodically.
AoE: Area of Effect; spells that have an area of effect from around the target or a radius from the caster.
Aggro - This term is short for "aggression" and it generally refers to the current attention of a mob. Whoever "has aggro" is the person currently being attacked by a mob.
Aggro Management - This is the process of maintaining hate or aggression levels so you control who a mob is attacking. Usually this means making sure the mob(s) is attacking the tank and not squishier targets like healers.
Buff: A temporary status effect that is generally beneficial. It raises or improves some stat or attribute.
CC - See Crowd Control.
Critical Hit - Critical hits are hits that do bonus damage due to the fact that they have hit a vulnerable spot. Typical critical hits in MMOs do double damage. Characters often have "critical hit rating" or "critical chance" which is their percent chance to deal a critical hit. Critical hits are generally very important for PvP as they deliver potent, much needed burst damage.
Crowd Control (CC) - This refers to the concept of mesmerizing, stunning, or otherwise "locking down" mobs or players so they are unable to act for a period of time. Early MMOs focused very heavily on crowd control as something necessary for success. WoW and more recent MMOs seem to ignore crowd control and focus more on pure DPS. This is a shame because crowd control is an interesting and challenging tactical element of combat in online games.
Debuff - A temporary status effect that lowers a statistic or other attribute of an opponent.
DoT - Damage over Time. This refers to an effect that deals damage in some portion smaller than the whole periodically. For example, a 50 damage DoT that was applied every 4 seconds for 40 seconds would deal a total of 500 damage (or 550 if it applied a tick of damage immediately as well at the end).
DPS (Damage Per Second) - The basic concept of DPS is simply a calculation of damage done per second. The term is also often used to refer to a certain type of class or player - someone playing a DPS class/character. A DPS class is a class designed with the primary role of dealing damage. DPS classes generally do not provide tanking, healing, or other significant forms of utility. In some games, however, DPS classes do provide utility, which generally throws off class balance enormously.
Experience Points - One of the most common methods of representing your character's "learning" is through the awarding of experience points. When you earn enough experience points, you either gain a level or you can spend the points on training.
HoT - Heal over Time. Powers of this type do not heal you all at once. Instead they apply some amount of healing periodically. For example, a HoT may heal you for 100 points of health every 10 seconds for a total of 10 ticks. That would mean 1000 health healed over 100 seconds.