Wisdom is hard to define. I have tried to define it a few times. Each time something is left out or neglected.
I am convinced that wisdom is not a virtue, but a collection of virtues. You could say that wisdom is a symphony of virtues all playing together the music of a life lived well.
I think my best definition so far is: Wisdom is mastery in the art of living. It is vague enough to incorporate multiple virtues, but specific enough to provide the aim of wisdom.
A sage, then, is a person who is skillful in the art of living.