ZENITH, n. The point in the heavens directly overhead to a man standing or a growing cabbage. A man in bed or a cabbage in the pot is not considered as having a zenith, though from this view of the matter there was once a considerable dissent among the learned, some holding that the posture of the body was immaterial. These were called Horizontalists, their opponents, Verticalists. The Horizontalist heresy was finally extinguished by Xanobus, the philosopher-king of Abara, a zealous Verticalist. Entering an assembly of philosophers who were debating the matter, he cast a severed human head at the feet of his opponents and asked them to determine its zenith, explaining that its body was hanging by the heels outside. Observing that it was the head of their leader, the Horizontalists hastened to profess themselves converted to whatever opinion the Crown might be pleased to hold, and Horizontalism took its place among fides defuncti.
2008 Update: The point of relative maximal ascendance, for example, the vice-presidency.