(1) To combine with oxygen; to add oxygen; to convert into an oxide.
(2) To remove hydrogen, as by the action of oxygen, e.g. to oxidise alcohol to form aldehyde.
(3) To increase the valence of an element, e.g. by removing electrons.
(4) To become oxidised.
When a compound is oxidised the oxidation number is increased. For instance, the suffix changes from –ous to –ic, such as mercurous chloride when oxidized becomes mercuric chloride.
Variant: oxidize (British)
Related forms: oxidises (simple present), oxidising (present participle), oxidised (simple past and past participle).
See also: oxidation.