Str
Project Lore EditorStrength, a base statistic
Stocks
The Stockade, an instance in Stormwind
Stam
Stamina, a base statistic
Stack
A number of identical items placed in a single bag slot, to conserve space. Only some items can be stacked. Also refers to multiple applications of a debuff or buff that increases its effects.
ST
Sunken Temple, also known as the Temple of Atal'Hakkar, an instance in Swamp of Sorrows
SSC
Serpentshrine Cavern, the Level 70 25-man raid instance of Coilfang Reservoir in Zangarmarsh
SS
Southshore. Also Soul Stone, a warlock's conjured item which allows a player to resurrect himself after he dies. Also Stormstrike, an Enhancement Shaman attack that causes the target to be vulnerable to nature damage.
SPI
Spirit, a base statistic
Spec
The allocation of talent points which determines how effective a character is at different roles
SP
Slave Pens, a Coilfang Reservoir instance in Zangarmarsh. Also, Shadow Priest. Also, Sunwell Plateau, a Level 70 25-man raid instance on the Isle of Quel'Danas