'O2' definitions:

Definition of 'O2'

From: GCIDE
  • Chromophore \Chro"mo*phore\, n. [Gr. ? color + fe`rein to bear.] (Chem.) Any chemical group or residue (as NO2; N2; or O2) which imparts some decided color to the compound of which it is an ingredient. [1913 Webster]