What does "sagacity" mean?

Sagacity: The quality of being sagacious; quickness or acuteness of sense perceptions; keenness of discernment or penetration with soundness of judgment; shrewdness. Some [brutes] show that nice sagacity of smell. Cowper. Natural sagacity improved by generous education. V. Knox. -- Sagacity, Penetration. Penetration enables us to enter into the depths of an abstruse subject, to detect motives, plans, etc. Sagacity adds to penetration a keen, practical judgment, which enables one to guard against the designs of others, and to turn everything to the best possible advantage.