The process of adding oxygen is called oxidation.
now if u consider the equation:
CH3-CH2-OH + KMnO4 => CH3-COOH
the number of oxygen atoms in product molecule or the resultant molecule is more than the num of oxygen atoms present at the reactant side.
so when ethanol is converted to ethanoic acid 1 oxygen atom gets added,this is nothing but oxidation process taking place.