Throw a snowball at Baine Bloodhoof during the Feast of Winter Veil.
IMPORTANT: Achievement can only be earned while Feast of Winter Veil is active.
Snowballs can be obtained from several sources. The best time and location is during Winter Veil at the Ruins of Alterac in Hillsbrad Foothills. There are oodles of Holiday Snow that contain snowballs. Snowballs are additionally sold by Smokywood Pastures vendors for 10 copper.
This achievement requires the (Horde) player to travel to Thunder Bluff. Baine Bloodhoof is located in the largest tent on the top tier of the main bluff.