The highest point of something; apex; summit; top: the vertex of a mountain.
Anatomy, Zoology. The crown or top of the head.
Craniometry. The highest point on the midsagittal plane of the skull or head viewed from the left side when the skull or head is in the Frankfurt horizontal.
Astronomy. A point in the celestial sphere toward which or from which the common motion of a group of stars is directed.
Geometry. A. The point farthest from the base: the vertex of a cone or of a pyramid. B. A point in a geometrical solid common to three or more sides. C. The intersection of two sides of a plane figure.
When the six-pointed star was laid perfectly over the Great Seal of the United States, the star's top vertex fit perfectly over the Masonic all-seeing eye…
-- Dan Brown, The Lost Symbol
Some way off from its near vertex (which happened to be between terrible Dino and Pemphredo the stinger), I hid behind a shrub of briar to reconnoiter…
-- John Barth, Chimera
Vertex stems from the Latin word of the same spelling which meant "a whirl" or "top (of the head)." It comes from the same stem as the word vortex, vert meaning "to turn." The sense of "the highest point" arose in the 1640s.