Very quick oxidation reactions result in combustion.
Reason
Oxidation reaction involved reaction with oxygen. Consider following example:
C6H12O6 + 6O2 → 6CO2 + 6H2O
(glucose) (carbon dioxide)
From the above reaction, it can be seen that, oxidation state of C in glucose in zero, while that in CO2 is +4. Thus, oxidation state of C is increased from 0 to +4. This process is called oxidation. Further, complete oxidation of reactant molecule is referred as combustion.