BoA - Binds on Account. You can't put it on the Auction House, but you can move it between your characters.
BoE - Binds on Equip. Trade-able. You can get it, pass it between your characters or resell it, up to when your character wears or uses some aspect of it.
BoP - Binds on Pickup - As soon as your character touches it, it's staying with them until you sell (not trade), use, salvage, or discard it.
Burn - refer to attack without a specific battle plan or without caring about the fight mechanic.
CTA - Call to Arms - a special version of existing skirmishes, typically with other special rewards attached to it
OP - Over-Powered or (related to forum posts) Original Poster. (Can also refer to the class Oathbound Paladin)
PE - Protector's Enclave
PVE - person versus environment -or- player versus environment
PVP - person versus person -or- player versus player
PUG - Pick up group, indicating groups created by random queue. Also used to indicate a team missing 1 or more components and accessing the queue to complete the team.
CN set - The weapon sets dropped from the Dracolich in Castle Never. Ancient Spymater(TR), Castle Champion(GWF), etc. A catch-all.
DL - Dread Legion weapons(Also armor, but less frequently)
FD - Fallen Dragon weapons
FF - Fabled Fomorian weapons
RBI - Raw Black Ice
Enchantments
Bark/BS - Barkshield
Bile/BT - Bilethorn
G - Greater
L - Lesser
P - Perfect
PF - Plague Fire
SF - Soulforged enchant
Vorp - Vorpal enchant
Example usages: GPF - Greater Plague Fire, highest level of PF; P.Vorp - Perfect Vorpal, LSF - Lesser Soulforged, P.Terror - Perfect Terror. I usually see the prefix-less versions of enchants referred to as 'normal', but I don't recall ever seeing an N used as abbreviation for this.