Please note that a definition must be so descriptive as to rule out any other possibilities. Suppose that a chemical reaction just took place. Suppose also that as a result of the reaction there was an increase in Gibbs Free Energy in the system.
Competitive inhibition involves competition for positioning in an active site.
An exergonic reaction drives an endergonic reaction. If the fit is not right, the reaction will probably not work. Since the enzyme only lowers the energy of activation delta G is NOT affected. Since the free energy of the reactants and the products is unchanged by an enzyme, delta G is NOT affected. Enthalpy will increase and entropy will decrease 15.