Loot

The treasure from a chest or a monster that has been killed, or the act of taking such treasure.

LOS

Line of Sight. Often used to mean breaking the line of sight between an NPC and a player, causing it to run towards the player.

Mag

Magtheridon's Lair. A 25-man raid instance of Hellfire Citadel

Mara

Maraudon, an instance in Desolace

Mech

The Mechanar, a Tempest Keep instance in Netherstorm

Mechanar

MgT

Magisters' Terrace, an instance on the Isle of Quel'Danas

MMO

Massively Multiplayer Online

MMOG

Massively Multiplayer Online Game

MMORPG

Massively Multiplayer Online Role Playing Game

MOB

From Mobile Object Block. Computer controlled character. Usually used in reference to any enemy NPC

MT

Main Tank. Also Mana-Tombs, an Auchindoun instance in Terokkar Forest. Also, miss tell, when a message is sent to the wrong person or channel on accident.

Named

A special monster that has a name instead of a generic descriptor. Usually stronger than surrounding monsters with possible special abilities and item drops.

Nerf

To reduce the effectiveness of a class, spell, ability, or item

Newb

Short for newbie, or new player. Suggests that a player is not very good

Newbie

A term that sometimes means new player. Newbie is also used to suggest that a player is not very good

Ninja

Taking an item, usually loot, without permission or agreement.

Noob

Short for newbie, or new player. Suggests that a player is not very good

NPC

Non player character. The characters are controlled by the server or realm. A "computer" character.

OMW

On My Way