What does this Acronym mean?

ACC = Accuracy
DET = Determination
DEX = Dexterity
iXXX = Item level of a piece of gear or average item level of a character's equipment (e.g. i140)
INT = Intelligence
MND = Mind
PIE = Piety
SS = Skill/Spell Speed
STR = Strength
VIT = Vitality

CD = Cooldown: An ability which has its own recast timer not shared with other abilities, and unaffected by Skill/Spell speed
DF = Duty Finder
DPS = Damage per second, also used to refer to damage dealing classes (i.e. not tanks or healers)
EX = Extreme mode; A very tough version of a trial with new mechanics and different loot.
FC = Free Company (aka Player-run guilds)
GC = Grand Company (Gridania's Twin Adders, Ul'dah's Immortal Flames and Limsa Lominsa's Maelstrom)
GCD = Global cooldown: An ability which shares its recast timer with other abilities. Higher Skill/Spell speed reduces the recast time.
GM = Game Master (aka Square Enix mods)
HM = Hard-mode; An advanced version of a trial or dungeon, usually as a sequel to the normal mode with tougher mechanics and different loot.
LB = Limit break
MGP = Manderville Gold Saucer Points (Currency for use in the Gold Saucer)
MSQ = Main story quest
OGCD: Synonym for Cooldown (CD).
PF = Party Finder

A[1-8] = Alexander (Lvl 60)
AK = Amdapor Keep (Lvl 50)
AV = Aurum Value (Lvl 47)
CC = Cutters Cry (Lvl 38)
CT = Crystal Tower: The collection of "Labyrinth of the Ancients", "Syrcus Tower" and "The World of Darkness"
HM = Haukke Manor (Lvl 28), can be confused with "Hard mode". There is also a Haukke Manor (Hard Mode), or "HMHM"
LotA = Labyrinth of the Ancients (Lvl 50)
ST = Syrcus Tower (Lvl 50)
SV = Stone Vigil (Lvl 41)
T[1-13] = The Binding Coil of Bahamut (Lvl 50)
WP = Wanderers' Palace (Lvl 50)
WoD = The World of Darkness (Lvl 50)