1. hydrogen peroxide, H2O2 or H–O–O–H.
  2. a compound containing the bivalent group –O2–, derived from hydrogen peroxide, as sodium peroxide, Na2O2, or dimethyl peroxide, C3H6O2.
  3. the oxide of an element that contains an unusually large amount of oxygen.

verb (used with object), per·ox·id·ed, per·ox·id·ing.

to use peroxide as a bleaching agent on (especially the hair).

Origin of peroxide

First recorded in 1795–1805; per- + oxide
Related formsper·ox·id·ic [pur-ok-sid-ik] /ˌpɜr ɒkˈsɪd ɪk/, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for peroxide

Contemporary Examples of peroxide

  • Covering her peroxide blond bob was a knit cap that sprouted an enormous feather and lace from its frontal lobe.

    The Daily Beast logo
    Head Over Heels for Hats

    The Daily Beast

    February 20, 2009

Historical Examples of peroxide

British Dictionary definitions for peroxide



short for hydrogen peroxide, esp when used for bleaching hair
any of a class of metallic oxides, such as sodium peroxide, Na 2 O 2, that contain the divalent ion O-O
(not in technical usage) any of certain dioxides, such as manganese peroxide, MnO 2, that resemble peroxides in their formula but do not contain the O-O ion
any of a class of organic compounds whose molecules contain two oxygen atoms bound together. They tend to be explosive
(modifier) of, relating to, bleached with, or resembling peroxide


(tr) to bleach (the hair) with peroxide
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for peroxide

1804, formed in English from per- "large amount" + oxide. Peroxide blonde is attested from 1918.

Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for peroxide




A compound, such as sodium peroxide, that contains a peroxy group and yields hydrogen peroxide when treated with an acid.
Hydrogen peroxide.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for peroxide



A compound containing the group O2. Peroxides are strong oxidizers and are used as industrial bleaches. When any peroxide is combined with an acid, one of the products is hydrogen peroxide.
Hydrogen peroxide.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.