Bloodlust is a 'spell,' or special ability, achievable by the Ogre units from the game Warcraft II. After a fairly decent amount of building and researching, each Ogre gains the ability to cast Bloodlust, for a small amount of mana, on one other, 'organic', unit, friend or foe. The effect of the spell is to increase the attack strength of the affected unit. This can make a group of nine ogres, a popular attack group, quite dangerous.
Bloodlust is regarded by many as the deciding strength of the Orc race that makes them better than the Humans overall. This is debateable.
Not many people play Warcraft these days, what with all the new games around (Starcraft, etc.). The nodeshell made me do it. :)