peroxide

n. 1 a = *hydrogen peroxide. B (often attrib.) Solution of hydrogen peroxide used esp. To bleach the hair. 2 compound of oxygen with another element containing the greatest possible proportion of oxygen. v. (-ding) bleach (the hair) with peroxide. [from *per-, *oxide]

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