Aggro

This means the monsters are mad at you and you've "activated" them to attack you. They are now in the motion of trying to reach and attack you. "The Murloc aggroed on me!" or "The Murlocs will aggro if you get too close!"

Derived from "aggresive". This means the monsters are mad at you and you've "activated" them to attack you. They are now in the motion of trying to reach and attack you.