In World of Warcraft, hostile can mean a couple of things:
- Hostile usually refers to a Player, Pet, NPC, Town, or City of an enemy faction to your character (Alliance or Horde) as opposed to being Friendly or of a Neutral faction.
- When you click on hostile mobs or NPCs, their name and highlight will be red. Most hostile creatures will attack your character when you get within a particular aggro or major threat range.
- Most mobs in hostile zones will be hostile.
- Neutral mobs or NPCs will turn hostile when attacked.
- You cannot talk to hostile creatures.
- Also the Reputation Level just below Unfriendly and above Hated.
- 3000 reputation points inside of being hostile.