Mob

In Guild Wars, players tend to use the term mob to refer to a foe or party of foes. Mob is simply a computer gaming term meaning "Mobile object", although in MMOs it also means NPC (see external link below).

Alliance Battles
Mobbing also refers to the Alliance Battle tactic of gathering together players from more than one party in order to overwhelm the opposing team. Also, mobs can refer to several separate groups of enemies that a player aggros into a large group, usually for another party member to nuke the enemies with area of effect damage.