Apex \A"pex\, n.; pl. E. {Apexes}; L. {Apices}. [L.] 1. The tip, top, point, or angular summit of anything; as, the apex of a mountain, spire, or cone; the apex, or tip, of a leaf. 2. (Mining) The end or edge of a vein nearest the surface. [U.S.] {Apex of the earth's motion} (Astron.), that point of the heavens toward which the earth is moving in its orbit.