Oxidant

n. oxidizing agent, oxidizer, agent or substance causing oxidization

An oxidizing agent (also called an oxidant or oxidizer) is A chemical compound that readily transfers oxygen atoms or A substance that gains electrons in a redox chemical reaction. The former definition is not applicable to what most people read about. It is also the sense that most organic chemists use the term. In both cases, the oxidizing agent becomes reduced in the process.
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Noun
1. a substance that oxidizes another substance
(synonym) oxidizer, oxidiser, oxidizing agent
(hypernym) chemical agent
(derivation) oxidize, oxidise, oxidate

A collective term for some of the primary constituents of photochemical smog.

Compare with reducing agent .An oxidizing agent is a substance that oxidizes another substance by removing electrons from it. Oxidizing agents cause other substances to be oxidized in chemical reactions while they themselves are reduced. For example, nitrate ion is an oxidizing agent in the following reaction:
Cu(s) + 4 H+(aq) + 2 NO3-(aq) Cu2+(aq) + 2 H2O() + 2 NO2(g)
Copper gets oxidized (its oxidation number goes from 0 to +2) while the nitrogen gets reduced (from +5 in nitrate to +4 in nitrogen dioxide).