Oxidative is used to describe winemaking techniques that expose a wine to oxygen, and it also applies to the aroma and flavour characteristics then present in the finished wine. Oxidative winemaking processes used judiciously help wines develop tertiary characteristics, but an excess of oxygen (such as a closure failing) results in a wine that smells and tastes like a Sherry (toasted nuts, caramel), and will be browner in colour than expected and lack fruit character.
This is the opposite end of the winemaking and flavour spectrum to reductive.
