peroxide

The divalent O2 group, or a compound containing this group, such as sodium peroxide, Na2O2, used as an oxidizing agent or bleach.

Hydrogen peroxide.

To treat with peroxide.

To bleach (hair) with hydrogen peroxide.

An oxide containing more oxygen than some other oxide of the same element. Formerly peroxides were regarded as the highest oxides. Cf. per-, 2.