Ork metabolism in the Games Workshop game Warhammer 40,000. It is the Waaagh! that drives orks to constantly wage war upon each other. In addition Waaagh! metabolism is closely connected with the orks latent psychic potential. That is, Waaagh! grows for each ork nearby so a large number of orks collectively has more Waaagh! Occasionally tides of orks gather under a particularly powerful warlord like the notorious Gazghkull mag uruk Thraka who laid waste to the Armageddon Sector and was only barely stopped by the combined effort of several Chapters of Space Marines and the Imperial hero Comissar Yarrick. A Waaagh! of this size is a threat to the entire galaxy and can only be dispersed by the slaying of the warlord or the killing of the bulk of the ork forces.
On a more interesting note, wa was an energy the samurai of Japan tried to harness. It was considered a calming, spiritual force. Waaagh! is clearly Games Workshop's adapted version of the Japanese wa.