ACC = Accuracy
ACN = Arcanist
AFK = Away From Keyboard
AK = Amdapor Keep; An easy-moderate difficulty level 50 dungeon that drops iLvl 60 gear. Very often repeated due to the fact that it gives the most Allagan Tomestones of Mythology (40) of any instance and the gear is a good intermediate between Artifact and Darklight gear.
ALC = Alchemist
AoE = Area of Effect: Abilities that do damage or inflict debuffs to multiple enemies
ARC = Archer
ARM = Armorer
ARR = A Realm Reborn
BCoB = The Binding Coil of Bahamut; As of 2.2, the most difficult instance in the game. The dungeon is split into 0 parts called "Turns".
BiS = Best in Slot; The single best item for a specific class / job to use in a specific gear slot (ie The +1 relic weapon is the best in slot weapon for many classes).
BLM = Black Mage
BRB = Be Right Back
BRD = Bard
BSM = Blacksmith
BTN = Botanist
CD = Cooldown of abilities
CM = Castrum Meridianum; The penultimate dungeon of the story line quests. A dungeon often repeated by high level players due to dropping 100 Tomestones of Philosophy and being relatively easy to clear quickly.
CNJ = Conjurer
Coil = The Binding Coil of Bahamut; As of 2.2, the most difficult instance in the game. The dungeon is split into 9 parts called "Turns".
Crit = Critical Hit
CRP = Carpenter
CT = Crystal Tower
CUL = Culinarian
DEF = Defense
DEX = Dexterity
DoH = Disciples of Hand; Classes that utilize crafting materials to create various items and gear (ALC, ARM, BSM, CLN, CRP, GSM, LTW, WVR).
DoM = Disciples of Magic; Battle classes that output primarily magic damage (ACN, CNJ, THM).
DoT = Damage over Time; An ability that deals consistent damage over a given amount of time to a target.
DoW = Disciples of War; Battle classes that output primarily physical damage (ARC, GLA, LNC, MRD, PGL).
DRG = Dragoon
EN = English: English speaking players
FATE = Full Active Time Event
FC = Free Company; The FFXIV iteration of a guild. A large collection of players that can communicate together. A Free Company can use company-wide bonuses such as EXP gain and reduced teleportation rates.
FFXIV = Final Fantasy XIV
FPS = Frames per second
FR = French: French speaking players
FSH = Fisher
GC = Grand Company; The 3 main military forces of Eorzea (The Immortal Flames, The Maelstrom, and The Order of the Twin Adder). You may join one of these forces and climb the ranks of the company after defeating Ifrit in the main story arc (lvl 20).
GCD = Global Cooldown - cooldown shared by multiple abilities
GG = Good Game
GH = Guildhest
GL = Guildleve
GM = Game Master
GLA = Gladiator
GSM = Goldsmith
HM = Hard Mode Trials or Dungeons; When appended to a Primal (Ifrit, Garuda and Titan), indicates a variation of the boss that is attainable at level 50. Hard mode variations are, as implied, increased difficulty and include more complex boss mechanics. These fights reward small amounts of Allagan Tomestones as well as a unique weapon.
HoT = Heal over Time; An ability that consistently heals a target over a given amount of time.
HP = HP
HQ = High Quality; A higher quality version of a craftable item or gear that will give higher stats than it's Normal Quality (NQ) counterpart. It is required that a crafter attain enough quality points in the crafting process to produce a High Quality item.
iLvl = Item Level; A property of a piece of gear that denotes the approximate effectiveness of the item. This is not the level required to equip the item. The highest item level of gear available at this time is iLvl 90.
INC = Incoming: warning for incoming enemies
INT = Intelligence
IRL = In Real Life
JP = Japanese: Japanese speaking players
LB = Limit Break; A powerful party ability in Final Fantasy that must be charged up prior to use and has varying effects depending on the class it is used by.
LF = Looking for; A common term used when searching for things or people. Variations include LFG, LFM and LFP being Looking For Group, Looking For More, and Looking For Party.
LoS = Line of Sight
LS = Link Shell; A permanent chat channel in which a collection of players can communicate together. Often formed to find players of similar interests with which you can play with together.
MB = Market Board
MIN = Miner
MND = Mind
MNK = Monk
Mob = Monster
MP = MP
MRD = Marauder
MT = Miss Tell, sending a whisper/tell to the wrong person. A previously sent message was sent to the wrong recipient or chat room.
Myth = Allagan Tomestones of Mythology; A currency used to purchase end-game gear and crafting materials. Obtained from completing high level dungeons. You can only obtain a maximum of 300 Allagan Tomestones of Mythology every week.
NPC = Non-Player Character
NQ = Normal Quality
OMW = On My Way
OOM = Out Of Mana/MP; Used to announce to allies that you are very low or completely out of MP.
PC = Player Character
PGL = Pugilist
PIE = Piety
PLD = Paladin
Pot = Potion
Prae = The Praetorium; The final dungeon of the story line quests featuring several boss battles. Although it also drops 100 Tomestones of Philosophy, it isn't farmed as often due to the fact that Castrum Meridianum is considerably faster if run with a group that is well geared and skips appropriate mobs.
PST = Please Send Tell; Used when asking replying parties to send a message via tell. Also onomatopoeia for a whisper; whispering is another terminology for sending a private in-game message used commonly in games.
PT = Party
PUG = Pick Up Group; Used to refer to a group of players that are found via /shout chat or even duty finder. Generally any group that wasn't already previously associated with each other. Often confused as Pugilist (PGL).
PvP = Player vs. Player - PvP activities are The Wolves' Den
Relic/Relic +1 = Relic Weapon/ Relic +1 Weapon; A very powerful weapon that is attained through a considerably long quest chain that takes you through end-game dungeons and boss fights, ending in defeating each of the Hard Mode Primals. 900 Allagan Tomestones of Philosophy are required to complete the relic weapon. Relic +1 is a stronger iteration of the relic weapon that can be attained once you have received the standard relic weapon and requires 3 Thavnarian Mists which can be purchased for 900 Allagan Tomestones of Mythology total.
RNG = Ranger or Random Number Generator
SCH = Scholar
SB = Spirit Bond
SCoB = The Second Coil of Bahamut
SE = Square Enix; The company that made Final Fantasy XIV A Realm Reborn.
SR = Speed Run; Appended to advertisements when arranging parties for instances, to indicate that you are looking to finish the dungeon as quickly as possible by taking shortcuts and skipping all possible enemies. Speed run groups often look for well-geared and experienced players to run through the dungeon even faster to maximize their gains by getting more dungeons completed.
STR = Strength
THM = Thaumaturge
TP = TP
VIT = Vitality
WAR = Warrior
WB = Welcome Back
WHM = White Mage
WP = The Wanderer's Palace; Entry-level level 50 dungeon that drops iLvl 55 gear. 50 Tomestones of Philosophy are obtained by completing the dungeon.
WS = Weaponskill
WTB = Wants to buy; Used when advertising that you are buying specific items or services from other players.
WTS = Wants to sell; Used when advertising that you are selling specific items or services from other players.
WVR = Weaver
Y = Yalm, an unit of distance in FFXIV