Aggro (WoW)  

The term aggro can be used to refer to three different related concepts.

1. Making initial contact with an enemy, by either angering them or simply drawing near enough to them to get their attention is often referred to as "aggroing" the target. Please stay along the right wall as we move to Lucifron or you will aggro the imps.
2. Threat is often sometimes referred to as aggro. The additional term "hate" is also sometimes used for this purpose. In World of Warcraft, Blizzard has been very consistent in using the term Threat for this purpose. While the threat article explains this more thoroughly, "building aggro" is act of generating threat toward a target so that they will attack you rather than another target. With some slight exception, the character with the most threat will be the one that is attacked. Don't attack for the first 10 seconds so the tank can get aggro.
3. The act of becoming the new target for an enemy. A player who does this is often said to be "ripping" or "pulling" aggro from the tank. This is usually something important for non-tanks to avoid. Everybody lived this time, except for Azuarc, because he was a noob that pulled aggro.

Outside the contexts of an MMORPG, aggro can also mean being highly aggressive. "Going aggro" is often likened to suddenly becoming berserk, and aggro decks in CCGs are decks that are meant to overrun the opponent very quickly.