Aggressive mob
Definition
Aggressive mobs are mobs that attack you immediately after becoming aware of your presence. In most cases, this is right when you enter a room, but it can also occur after some sort of trigger, such as waking the mob up or drawing it's attention. In some scenarios, an aggressive mob may not be aware of your presence because you are hidden or invisible and it has no means of detecting you (IE detect invis).
Examples
It is safe to assume that most mobs that you run across inside a dungeon or other dangerous location will be aggressive. Many big run mobs are aggressive, such as Legba.
See Also: Neutral mob, Pacifist mob.