TB
Thunder Bluff, home of the Tauren
Threat
A value which determines who an NPC is attacking or focusing on. Once a player has aggro, other players in melee range need to reach 110% of that player's threat to take the aggro of the NPC. Players outside of melee ranged need to reach 130% to pull aggro.
Tier
Refers to a level of raiding content or class specific equipment. Tiers 1-3 are acquired in level 60 raid encounters, whereas T4-6 are in level 70 raids.
TK
Tempest Keep, a group of instances in Netherstorm. Sometimes refers to The Eye, the Level 70 25-man raid wing of Tempest Keep.
Trash
Enemies in an instance that are not bosses. In raids, trash will respawn after a certain amount of time if the associated boss is not killed.
Twink
A low level character who has been made more powerful by higher level characters, usually by getting stronger armor and weapons than the character would normally have at such a low level. Twinks usually have levels ending in 9 in order to dominate battlegrounds.
UA
Unstable affliction. A 41-point warlock talent in the affliction tree, a DoT that causes damage to anyone who dispels it.
UB
The Underbog, a Coilfang Reservoir instance in Zangarmarsh
Uber
German slang for 'super', originally meaning 'over'; exceptionally powerful
UC
Undercity, home of the Undead
Uld
Uldaman, an instance in Badlands
VW
Voidwalker, a tanking pet used by warlocks
WC
Wailing Caverns, an instance in the Barrens.
WF
Westfall, a zone in the Eastern Kingdoms. Also Windfury, either the spell or totem cast by Shaman which produces extra attacks upon proc.
Wipe
When an entire group dies during an encounter, usually in an instance or raid.
WotLK
Wrath of the Lich King, the not yet released second expansion for World of Warcraft
WoW
World of Warcraft
WSG
Warsong Gulch, a 10-man battleground where the objective is to capture the opposition's flag.
WTB
Want to Buy
WTS
Want to Sell