What is a MMO?

MMO, is an abbreviation of Massively Multiplayer Online. In practice the term is pretty much always used for some sort of game, even though some of the games may be more of a virtual world than a game per se.
The most common type of MMO is probably the MMORPG, Massively Multiplayer Online Roleplaying Game. Quite understandably, most people feel that MMO is a more handy term for them...

A MMO is in short an online game with several hundred players interacting simultaneously

This site is dedicated to a few of them that we play or know well.

MMO Dictionary

A

add	when a monster, or a player, "adds" to a fight in progress. - Run, we got adds
ae, aoe	area of effect, something, usually a magic spell affects things in a radius around the target - Aoe dot ftw!
afk	away from keyboard - afk one minute
aggro	when a monster becomes actively aggressive and starts to attack - Hug the wall so we don't get aggro!
alt	alternate character, if you have several characters they are called alts - How many alts do you have?!
assist	often it is beneficial if all players assist on a single target, thereby killing it faster - Assist, assist!
atm	at the moment - sorry not atm
avatar	your character in the game

B

bbl	be back later - I have to make dinner now, bbl
bio	basic input/output or biological - I need a bio break!
bot	a character not actively played, commonly used for buffing - can I bum some buffs from your bot?
brb	be right back - Just need to visit the merchant, brb
brt	be right there - Hang on, brt
buff	a magic spell that enhances some aspect of your character - I'm missing dex buff

C

cc	crowd control, means to immobilize enemy players or monsters - don't break the cc
crit , chit	critical hit, usually you have a small chance to land a critical hit that does extra damage - must have been a crit

D

dd	direct damage, magic that delivers damage directly as opposed to a dot
dot	damage over time, damage being delivered over a duration of time after the initial attack
dps	damage per second

E

emote

command used to express feelings and gestures, used instead of "say". Might result in the character doing a special animation

F

ftw	for the win

G

gank	means different things to different players, but in general if you gank someone it means it isn't a fair fight
gfx	graphics
grief	for example stalking someone who is trying to do a quest and killing them over and over and over

H

hot	heal over time, healing of hitpoints delivered over a duration of time after the spell is cast

I

irl	in real life - where do you live irl?

K

kite	a combat tactic where the attacker slowly kills the defender while staying out of reach

L

lag	overall a sluggish reaction to given commands, also frequently used to describe low frame rates
ld	linkdead, when the player for one reason or the other looses contact with the server
leet, l33t	elite
lfg	looking for group
lol	laughing out loud
los	line of sight
loot	reward in form of items or currency, usually found on a killed monster

M

mez	mesmerize, a magic ability rendering the enemy unable to take any action, unless hit, for some time
mob	usually refers to a non player character / monster. similar to npc
mt	mistell, accidentally sending a message where you didn't intend to
mud	multi user dungeon, a text based predecessor to mmo

N

nerf	when an ability or item is made less effective
ninja	to steal loot
newbie, noob, n00b	inexperienced or unskilled player, newbie has the kinder, softer, meaning of the two
np	no problem
npc	non player character

O

omg	oh my god
omw	on my way
ooc	out of character, used by a roleplayer if he/she temporarily need to go out of character - (ooc) Having a gfx glitch

P

proc	programmed random occurrence, for instance a weapon my occasionally "proc" poison when it hits the enemy
pull	to attract the attention of the enemy and have it attack you
pve	player versus environment, interacting with anything that isn't another player
pvp	player versus player, combat with another player
pwn	used similar to own, "dominating"

Q

QQ	Used to imply crying or whining

R

rez	resurrect
reroll	start over from scratch with a new character
rofl	rolling on the floor laughing
root	magic ability making the enemy unable to move, but still able to do anything else

T

tank	a character being able to take heavy damage, especially melee damage
tard	retard
tell	private communication from one player to another
toon	your character in the game

W

woot	used to express being excited in a happy way - woot, finally level 50!

Z

zerg	a large number of mobs or players