superoxide

from WordNet (r) 3.0 (2006)

superoxide
    n 1: a metallic oxide containing the univalent anion O2-
    2: the univalent anion O2-; "much of the O2 supporting cellular
       respiration is reduced to the superoxide anion O2-" [syn:
       {superoxide}, {superoxide anion}]

from The Collaborative International Dictionary of English v.0.48

Superoxide \Su`per*ox"ide\, n. (Chem.)
   See {Peroxide}. [Obs.]
   [1913 Webster]