Aggro

Aggro is a slang term meaning "to cause hostile NPC mobs to attack by getting too close to them." Short for "Aggravate". The mini-map located in the upper right hand corner of the screen displays a white transparent circle that surrounds your character. Any mob (indicated by red dots) that even slightly enters this circle (often called your "aggro bubble" or "aggro circle") immediately becomes aware of your presence and is aggravated, causing it to attack you. Careful understanding and awareness of your bubble is very important, especially if your teammates are low on health/energy or already attacking another group of enemies. A target "breaks aggro" when it disengages and stops attacking, although it may still be in the aggro bubble when this happens. Several things can cause an enemies to break aggro including using AoE skills such as Fire Storm or running away and activating a running skill like Sprint.