1. Enemy of Samus Aran in the Metroid games "Metroid" and "Super Metroid," Mother Brain is the presumed leader of the Space Pirates and, together with her winged colleague, Ridley, poses a great threat to the Galactic Federation. Armed with her vast intelligence, she seeks to manipulate the power of the Metroids to her advantage.
Typically depicted as resting immobile in an armored case, Mother Brain has also developed other means of defending herself. In "Super Metroid" she demonstrated her combat ability through an enormous bio-mechanical bipedal body- the use of which granted her the mobility she needed to bring her energy beams and bombs to bear against Samus.
Mother Brain was responsible for the slaughter of the "daughter Metroid" of Samus Aran at that same confrontation, adding to the acridness in the feud between the two.
2. an intelligent, reclusive person who remains somewhat guarded and isolated; tends to shy away from those less intelligent than them