Used in reference to a decision or action that gaming company Blizzard Entertainment have done wrong in the eyes of their customers.
Most often as a reaction to glitches or bugs in their games that have resulted in the failure of the player to achieve a goal through no fault of their own.
(also see "gg blizz
WTF blizz, the quest is bugged i cant talk to the NPC.
Fking boss keeps reseting at 10% WTF blizz
WTF BLIZZ DRUIDS NERFED AGAIN?!?!