Pareto optimal: A solution in a multiobjective optimization problem which satisfies the Pareto-efficiency criterion. Equivalent to the term "Pareto-efficient". Applied to the efficient allocation of resources, Pareto optimality is achieved when it is impossible to change an allocation that would increase the satisfaction of some people without reducing the satisfaction of some others. In the case of income distribution, a pareto optimal income distribution is one which cannot be changed to make one individual better off without making at least one other individual worse off.